libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

amazon_alas ALAS2023-2026-1928: Amazon Linux 2023 Security Advisory:ALAS2023-2026-1928

The version of firefox installed on the remote host is prior to 140.12.0-1. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2FIREFOX-2026-062 advisory.

    Privilege escalation in the Graphics: WebRender component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12289)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12290)

    Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12291)

    Incorrect boundary conditions in the Web Audio component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12292)

    Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12294)

    Sandbox escape in the DOM: Navigation component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12295)

    Sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12296)

    Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was     fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
    (CVE-2026-12297)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12298)

    JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox     ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12299)

    Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12302)

    Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox     152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12304)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12305)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12306)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12307)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12308)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12309)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12310)

    Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability     was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12311)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12312)

    Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability     was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12313)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12314)

    Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12315)

    Incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in     Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12324)

    Denial-of-service in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12325)

    Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151.
    Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of     these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12327)

    Memory safety bugs present in Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151     and Thunderbird 151. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed     in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
    (CVE-2026-12328)

    Memory safety bug fixed in Thunderbird ESR 140.12. This vulnerability was fixed in Firefox ESR 140.12 and     Thunderbird 140.12. (CVE-2026-12329)

    Incorrect boundary conditions in the Internationalization component. This vulnerability was fixed in     Firefox ESR 140.12, Firefox ESR 115.37, and Thunderbird 140.12. (CVE-2026-12330)

    libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,     XML_ParseBuffer, XML_ParserFree, or XML_ParserReset from within handlers in cases of a policy violation.
    Thus, a use-after-free can occur, (CVE-2026-50219)

    libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers     in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219     situation). (CVE-2026-56131)

    In libexpat before 2.8.2, there is a heap-based buffer overflow in doProlog in xmlparse.c because scaffold     backing array reallocation is mishandled when there is data-structure sharing across parsers.
    (CVE-2026-56132)

    A heap buffer overflow vulnerability was found in libaom, the reference AV1 codec implementation. A flaw     in the AV1 encoder's Look-Ahead Processing (LAP) mode causes the first-pass stats ring buffer wrap-around     guard to be bypassed when g_lag_in_frames is set to 1 or higher. This results in a 232-byte out-of-bounds     write on every encoded frame after the second, corrupting adjacent heap objects. An attacker who can     influence encoder configuration in a transcoding service or WebRTC session could exploit this to cause a     denial of service (process crash) or potentially achieve code execution. (CVE-2026-56208)

    A heap-buffer-overflow read vulnerability was found in libaom, the reference AV1 codec implementation. A     missing bounds check in the SVC (Scalable Video Coding) layer ID control function allows setting a     spatial_layer_id exceeding the configured number of layers. This causes an out-of-bounds heap read of     approximately 40,728 bytes when computing a layer context array index. An attacker who can influence SVC     encoder parameters in a network-facing service could exploit this for information disclosure (heap content     leak) or denial of service (segmentation fault from hitting unmapped memory). (CVE-2026-56210)

    A remote code execution vulnerability was found in libaom, the reference AV1 codec implementation.
    Insufficient bounds validation in the AV1 encoder's SVC (Scalable Video Coding) layer ID control allows an     attacker to supply crafted video frame pixels that overlap with internal encoder layer context structures.
    In fork-based video processing services, an attacker can use this to hijack the cyclic refresh map     pointer, brute-force the process base address via a crash oracle, and redirect control flow to achieve     arbitrary command execution. Exploitation requires the target service to use libaom with SVC encoding     enabled and accept attacker-supplied video frames. (CVE-2026-56211)

    libexpat before 2.8.2 has an integer overflow in storeAtts. (CVE-2026-56403)

    libexpat before 2.8.2 has an integer overflow in addBinding. (CVE-2026-56404)

    libexpat before 2.8.2 has an integer overflow in getAttributeId. (CVE-2026-56405)

    libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was     present in XML_Parse. (CVE-2026-56406)

    libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity     textLen. (CVE-2026-56407)

    libexpat before 2.8.2 has an integer overflow in copyString. (CVE-2026-56408)

    libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call     depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-     free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219. (CVE-2026-56412)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of thunderbird installed on the remote host is prior to 140.12.0-1. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3795 advisory.

    Privilege escalation in the Graphics: WebRender component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12289)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12290)

    Incorrect boundary conditions in the Web Audio component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12292)

    Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12294)

    Sandbox escape in the DOM: Navigation component. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12295)

    Sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12296)

    Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was     fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
    (CVE-2026-12297)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12298)

    JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox     ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12299)

    Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox     152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12304)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12305)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12306)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12307)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12308)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12309)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12310)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12312)

    Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability     was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12313)

    Memory safety bug fixed in Thunderbird 152. This vulnerability was fixed in Firefox 152, Firefox ESR     140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12314)

    Incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in     Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12324)

    Denial-of-service in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12325)

    Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151.
    Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of     these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 152,     Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12. (CVE-2026-12327)

    Memory safety bugs present in Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151     and Thunderbird 151. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed     in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
    (CVE-2026-12328)

    Memory safety bug fixed in Thunderbird ESR 140.12. This vulnerability was fixed in Firefox ESR 140.12 and     Thunderbird 140.12. (CVE-2026-12329)

    Incorrect boundary conditions in the Internationalization component. This vulnerability was fixed in     Firefox ESR 140.12, Firefox ESR 115.37, and Thunderbird 140.12. (CVE-2026-12330)

    libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,     XML_ParseBuffer, XML_ParserFree, or XML_ParserReset from within handlers in cases of a policy violation.
    Thus, a use-after-free can occur, (CVE-2026-50219)

    libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers     in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219     situation). (CVE-2026-56131)

    In libexpat before 2.8.2, there is a heap-based buffer overflow in doProlog in xmlparse.c because scaffold     backing array reallocation is mishandled when there is data-structure sharing across parsers.
    (CVE-2026-56132)

    A heap buffer overflow vulnerability was found in libaom, the reference AV1 codec implementation. A flaw     in the AV1 encoder's Look-Ahead Processing (LAP) mode causes the first-pass stats ring buffer wrap-around     guard to be bypassed when g_lag_in_frames is set to 1 or higher. This results in a 232-byte out-of-bounds     write on every encoded frame after the second, corrupting adjacent heap objects. An attacker who can     influence encoder configuration in a transcoding service or WebRTC session could exploit this to cause a     denial of service (process crash) or potentially achieve code execution. (CVE-2026-56208)

    A heap-buffer-overflow read vulnerability was found in libaom, the reference AV1 codec implementation. A     missing bounds check in the SVC (Scalable Video Coding) layer ID control function allows setting a     spatial_layer_id exceeding the configured number of layers. This causes an out-of-bounds heap read of     approximately 40,728 bytes when computing a layer context array index. An attacker who can influence SVC     encoder parameters in a network-facing service could exploit this for information disclosure (heap content     leak) or denial of service (segmentation fault from hitting unmapped memory). (CVE-2026-56210)

    A remote code execution vulnerability was found in libaom, the reference AV1 codec implementation.
    Insufficient bounds validation in the AV1 encoder's SVC (Scalable Video Coding) layer ID control allows an     attacker to supply crafted video frame pixels that overlap with internal encoder layer context structures.
    In fork-based video processing services, an attacker can use this to hijack the cyclic refresh map     pointer, brute-force the process base address via a crash oracle, and redirect control flow to achieve     arbitrary command execution. Exploitation requires the target service to use libaom with SVC encoding     enabled and accept attacker-supplied video frames. (CVE-2026-56211)

    libexpat before 2.8.2 has an integer overflow in storeAtts. (CVE-2026-56403)

    libexpat before 2.8.2 has an integer overflow in addBinding. (CVE-2026-56404)

    libexpat before 2.8.2 has an integer overflow in getAttributeId. (CVE-2026-56405)

    libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was     present in XML_Parse. (CVE-2026-56406)

    libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity     textLen. (CVE-2026-56407)

    libexpat before 2.8.2 has an integer overflow in copyString. (CVE-2026-56408)

    libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call     depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-     free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219. (CVE-2026-56412)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call
    depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-
    free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219. (CVE-2026-56412)

  - libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,
    XML_ParseBuffer, XML_ParserFree, or XML_ParserReset from within handlers in cases of a policy violation.
    Thus, a use-after-free can occur, (CVE-2026-50219)

  - libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers
    in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219
    situation). (CVE-2026-56131)

  - In libexpat before 2.8.2, there is a heap-based buffer overflow in doProlog in xmlparse.c because scaffold
    backing array reallocation is mishandled when there is data-structure sharing across parsers.
    (CVE-2026-56132)

  - libexpat before 2.8.2 has an integer overflow in storeAtts. (CVE-2026-56403)

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the d06b1fa2-731f-11f1-a0d2-589cfc10a551 advisory.

    Expat 2.8.2 was released yesterday. The key motivation for cutting a release and doing so now was     getting security and non-security bugsfixes out to users. On the security side,     13 vulnerabilities have been fixed:

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers     in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219     situation). (CVE-2026-56131)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
325581	Amazon Linux 2 : firefox, --advisory ALAS2FIREFOX-2026-062 (ALASFIREFOX-2026-062)	Nessus	Amazon Linux Local Security Checks	medium
325578	Amazon Linux 2 : thunderbird, --advisory ALAS2-2026-3795 (ALAS-2026-3795)	Nessus	Amazon Linux Local Security Checks	medium
444103	Alpine: libexpat, multiple expat packages: security update to 2.8.2-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	medium
444103	Alpine: libexpat, multiple expat packages: security update to 2.8.2-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	medium
323688	FreeBSD : Multiple vulnerability found in Expat (d06b1fa2-731f-11f1-a0d2-589cfc10a551)	Nessus	FreeBSD Local Security Checks	medium
321769	Linux Distros Unpatched Vulnerability : CVE-2026-56131	Nessus	Misc.	medium

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