xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2157 advisory.

    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)

    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 copyString. (CVE-2026-56408)

    xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.
    (CVE-2026-56409)

    xmlwf in libexpat before 2.8.2 has an integer overflow in resolveSystemId. (CVE-2026-56410)

    xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION declarations.
    (CVE-2026-56411)

    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)

    Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity     in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized     values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote     unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application     parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring     authentication, external entity resolution, or non-default parser options. (CVE-2026-66046)

    libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after-     free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.
    (CVE-2026-76957)

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.

According to the versions of the expat packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    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)

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

    xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION     declarations.(CVE-2026-56411)

    xmlwf in libexpat before 2.8.2 has an integer overflow in resolveSystemId.(CVE-2026-56410)

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

    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 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 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 getAttributeId.(CVE-2026-56405)

    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)

    xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is     used.(CVE-2026-56409)

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

    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)

Tenable has extracted the preceding description block directly from the EulerOS expat 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 remote Debian 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4765 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4765-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                       Andrej Shadura     August 31, 2026                               https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : expat     Version        : 2.5.0-1+deb12u3     CVE ID         : CVE-2026-50219 CVE-2026-56131 CVE-2026-56403                      CVE-2026-56404 CVE-2026-56405 CVE-2026-56406                      CVE-2026-56407 CVE-2026-56408 CVE-2026-56409                      CVE-2026-56410 CVE-2026-56411 CVE-2026-56412                      CVE-2026-72522 CVE-2026-76957

    CVE-2026-50219, CVE-2026-56131, CVE-2026-76957

        Calling certain libexpat functions from within a handler could cause         use-after-free.

    CVE-2026-56403, CVE-2026-56404, CVE-2026-56405, CVE-2026-56406,     CVE-2026-56407, CVE-2026-56408, CVE-2026-56409, CVE-2026-56410,     CVE-2026-56411

        Integer overflow in several functions.

    CVE-2026-56412

        A missing reentrancy guard around CDATA section handler calls could         cause use-after-free.

    CVE-2026-72522

        An out-of-bounds read in expat's internal UTF-16 conversion functions         could cause an infinite loop when processing crafted input, resulting         in a denial of service.

    For Debian 12 bookworm, these problems have been fixed in version     2.5.0-1+deb12u3.

    We recommend that you upgrade your expat packages.

    For the detailed security status of expat please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/expat

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian 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 Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-099515 advisory.

    xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.

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

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

The remote Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6404 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6404-1                   security@debian.org     https://www.debian.org/security/                                  Aron Xu     July 30, 2026                         https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : expat     CVE ID         : CVE-2025-59375 CVE-2026-24515 CVE-2026-25210 CVE-2026-32776                      CVE-2026-32777 CVE-2026-32778 CVE-2026-41080 CVE-2026-45186                      CVE-2026-50219 CVE-2026-56131 CVE-2026-56132 CVE-2026-56403                      CVE-2026-56404 CVE-2026-56405 CVE-2026-56406 CVE-2026-56407                      CVE-2026-56408 CVE-2026-56409 CVE-2026-56410 CVE-2026-56411                      CVE-2026-56412

    Multiple security issues were discovered in expat, an XML parsing C library,     including integer overflows, out-of-bounds write, NULL pointer dereferences,     excessive resource consumption, and memory corruption through re-entrant     parser API calls, which may result in denial of service or potentially the     execution of arbitrary code.

    For the stable distribution (trixie), this problem has been fixed in     version 2.8.2-1~deb13u1.

    We recommend that you upgrade your expat packages.

    For the detailed security status of expat please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/expat

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian 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.

  - xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.
    (CVE-2026-56409)

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

ID	Name	Product	Family	Type	Severity
345784	Amazon Linux 2023 : expat, expat-devel, expat-static (ALAS2023-2026-2157)	Nessus	Amazon Linux Local Security Checks	Local	high
343660	EulerOS 2.0 SP12 : expat (EulerOS-SA-2026-3333)	Nessus	Huawei Local Security Checks	Local	medium
343618	EulerOS 2.0 SP12 : expat (EulerOS-SA-2026-3258)	Nessus	Huawei Local Security Checks	Local	medium
341830	Debian dla-4765 : expat - security update	Nessus	Debian Local Security Checks	Local	high
336997	Unity Linux 20.1070e Security Update: expat (UTSA-2026-099515)	Nessus	Unity Linux Local Security Checks	Local	medium
330837	Debian dsa-6404 : expat - security update	Nessus	Debian Local Security Checks	Local	high
444103	Alpine: libexpat, multiple expat packages: security update to 2.8.2-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	medium
444103	Alpine: libexpat, multiple expat packages: security update to 2.8.2-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	medium
323688	FreeBSD : Multiple vulnerability found in Expat (d06b1fa2-731f-11f1-a0d2-589cfc10a551)	Nessus	FreeBSD Local Security Checks	Local	medium
321889	Linux Distros Unpatched Vulnerability : CVE-2026-56409	Nessus	Misc.	Local	medium

Detections

Analytics

CVE-2026-56409

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Tenable Plugins

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