In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of service via crafted XML content.

The remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:23912-1 advisory.

    - CVE-2026-41080: crafted XML document can cause a denial of service (bsc#1262263).
    - CVE-2026-45186: In libexpat before 2.8.1, the computational complexity of attribute name collision     checks allows a       denial of service via moderately sized crafted XML input (bsc#1264713).
    - CVE-2026-50219: 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     (bsc#1267631).
    - CVE-2026-56131: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser     from within       handlers in cases of a policy violation (bsc#1268572).
    - CVE-2026-56132: mishandled memory reallocation during array scaffolding in doProlog can cause heap-based     buffer       overflows (bsc#1268573).
    - CVE-2026-56403: integer overflow in the storeAtts function can cause memory corruption and potential     arbitrary code       execution (bsc#1275096).
    - CVE-2026-56404: integer overflow in the addBinding function can cause undersized memory allocations,     memory       corruption, and application crashes (bsc#1275096).
    - CVE-2026-56405: integer overflow in the getAttributeId function can cause heap memory corruption and     arbitrary       code execution (bsc#1275096).
    - CVE-2026-56406: missing bounds validation in XML_ParseBuffer can cause integer overflows, memory     corruption, and       application crashes (bsc#1275096).
    - CVE-2026-56407: integer overflow in doProlog related to entity text length can cause memory corruption     and denial       of service (bsc#1275096).
    - CVE-2026-56408: integer overflow in the copyString function can cause heap memory corruption and     application crashes       (bsc#1275096).
    - CVE-2026-56409: integer overflow in the xmlwf utility output filename handling can allow path buffer     corruption and       arbitrary file write conditions (bsc#1275096).
    - CVE-2026-56410: integer overflow in resolveSystemId within the xmlwf utility can cause memory     corruption, information       disclosure, and potential code execution (bsc#1275096).
    - CVE-2026-56411: integer overflow in endDoctypeDecl via NOTATION declarations in xmlwf can cause memory     corruption and       denial of service (bsc#1275096).
    - CVE-2026-56412: incomplete handler call depth tracking in doCdataSection can cause use-after-free       conditions and arbitrary code execution (bsc#1275096).
    - CVE-2026-66046: libexpat: denial of service vulnerability caused by quadratic algorithmic complexity in     the       storeAtts() function in xmlparse.c (bsc#1275732).
    - CVE-2026-72522: libexpat: out-of-bounds read and resultant infinite loop due to low surrogates being     treated the same       as high surrogates during Unicode processing (bsc#1275594).
    - CVE-2026-76641: Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers     to trigger       memory corruption (bsc#1275915).
    - CVE-2026-76956: In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code     leads to       insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of     service via       crafted X (bsc#1275860).
    - CVE-2026-76957: libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks.
    (bsc#1275859).

    Changes for expat:

    - Updated to version 2.8.4

Tenable has extracted the preceding description block directly from the SUSE 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 openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21945-1 advisory.

    - CVE-2026-41080: crafted XML document can cause a denial of service (bsc#1262263).
    - CVE-2026-45186: In libexpat before 2.8.1, the computational complexity of attribute name collision     checks allows a       denial of service via moderately sized crafted XML input (bsc#1264713).
    - CVE-2026-50219: 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     (bsc#1267631).
    - CVE-2026-56131: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser     from within       handlers in cases of a policy violation (bsc#1268572).
    - CVE-2026-56132: mishandled memory reallocation during array scaffolding in doProlog can cause heap-based     buffer       overflows (bsc#1268573).
    - CVE-2026-56403: integer overflow in the storeAtts function can cause memory corruption and potential     arbitrary code       execution (bsc#1275096).
    - CVE-2026-56404: integer overflow in the addBinding function can cause undersized memory allocations,     memory       corruption, and application crashes (bsc#1275096).
    - CVE-2026-56405: integer overflow in the getAttributeId function can cause heap memory corruption and     arbitrary       code execution (bsc#1275096).
    - CVE-2026-56406: missing bounds validation in XML_ParseBuffer can cause integer overflows, memory     corruption, and       application crashes (bsc#1275096).
    - CVE-2026-56407: integer overflow in doProlog related to entity text length can cause memory corruption     and denial       of service (bsc#1275096).
    - CVE-2026-56408: integer overflow in the copyString function can cause heap memory corruption and     application crashes       (bsc#1275096).
    - CVE-2026-56409: integer overflow in the xmlwf utility output filename handling can allow path buffer     corruption and       arbitrary file write conditions (bsc#1275096).
    - CVE-2026-56410: integer overflow in resolveSystemId within the xmlwf utility can cause memory     corruption, information       disclosure, and potential code execution (bsc#1275096).
    - CVE-2026-56411: integer overflow in endDoctypeDecl via NOTATION declarations in xmlwf can cause memory     corruption and       denial of service (bsc#1275096).
    - CVE-2026-56412: incomplete handler call depth tracking in doCdataSection can cause use-after-free       conditions and arbitrary code execution (bsc#1275096).
    - CVE-2026-66046: libexpat: denial of service vulnerability caused by quadratic algorithmic complexity in     the       storeAtts() function in xmlparse.c (bsc#1275732).
    - CVE-2026-72522: libexpat: out-of-bounds read and resultant infinite loop due to low surrogates being     treated the same       as high surrogates during Unicode processing (bsc#1275594).
    - CVE-2026-76641: Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers     to trigger       memory corruption (bsc#1275915).
    - CVE-2026-76956: In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code     leads to       insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of     service via       crafted X (bsc#1275860).
    - CVE-2026-76957: libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks.
    (bsc#1275859).

    Changes for expat:

    - Updated to version 2.8.4

Tenable has extracted the preceding description block directly from the SUSE 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 Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-5660612c34 advisory.

    Update to expat-2.8.4.

Tenable has extracted the preceding description block directly from the Fedora 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 Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-4a2ee61320 advisory.

    Update to expat-2.8.4.

Tenable has extracted the preceding description block directly from the Fedora 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 Fedora 45 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-9e9244744d advisory.

    Update to expat-2.8.4.

    ----

    Update to expat-2.8.3.

Tenable has extracted the preceding description block directly from the Fedora 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:

  - 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)

  - Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory
    corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A
    struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past
    allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a
    wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for
    CVE-2026-66046. (CVE-2026-76641)

  - In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to
    insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of
    service via crafted XML content. (CVE-2026-76956)

  - 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)

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

  - In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to     insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of     service via crafted XML content. (CVE-2026-76956)

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

ID	Name	Product	Family	Type	Severity
351397	SUSE SLES16 Security Update : expat (SUSE-SU-2026:23912-1)	Nessus	SuSE Local Security Checks	Local	high
350766	openSUSE 16 Security Update : expat (openSUSE-SU-2026:21945-1)	Nessus	SuSE Local Security Checks	Local	high
344990	Fedora 44 : mingw-expat (2026-5660612c34)	Nessus	Fedora Local Security Checks	Local	high
344988	Fedora 43 : mingw-expat (2026-4a2ee61320)	Nessus	Fedora Local Security Checks	Local	high
344891	Fedora 45 : mingw-expat (2026-9e9244744d)	Nessus	Fedora Local Security Checks	Local	high
447379	Alpine: libexpat, multiple expat packages: security update to 2.8.4-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	high
447379	Alpine: libexpat, multiple expat packages: security update to 2.8.4-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	high
338289	Linux Distros Unpatched Vulnerability : CVE-2026-76956	Nessus	Misc.	Local	high

Detections

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CVE-2026-76956

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Tenable Plugins

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high