In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow.

An update of the libxml2 package has been released.

The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8910-1 advisory.

    Yirou Yang discovered that libxml2 incorrectly handled certain XML catalogs. If a user or automated system     was tricked into processing a specially crafted XML catalog, an attacker could possibly use this issue to     cause libxml2 to crash, resulting in a denial of service. (CVE-2026-76781)

    It was discovered that libxml2 incorrectly handled certain large qualified names, leading to a heap-based     buffer overflow. An attacker could possibly use this issue to cause libxml2 to crash, resulting in a     denial of service, or possibly execute arbitrary code. (CVE-2026-86138)

    It was discovered that libxml2 incorrectly handled escaping certain large URI strings. An attacker could     possibly use this issue to cause libxml2 to use excessive resources, leading to a denial of service. This     issue only affected Ubuntu 26.04 LTS. (CVE-2026-86139)

    Xudong Cao and Meng Xu discovered that libxml2 incorrectly handled certain large XPointer expressions,     leading to a heap-based buffer overflow. An attacker could possibly use this issue to cause libxml2 to     crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-86142)

    Xudong Cao and Meng Xu discovered that libxml2 did not check for integer overflows before passing output     lengths to write callbacks. An attacker could possibly use this issue to cause an application using     libxml2 to crash, resulting in a denial of service. (CVE-2026-86143)

    It was discovered that libxml2 did not apply parser options, such as disabling network access, when     processing XInclude directives under certain circumstances. An attacker could possibly use this issue to     perform XML external entity injection or server-side request forgery attacks, or cause a denial of     service. (CVE-2026-86144)

Tenable has extracted the preceding description block directly from the Ubuntu 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 a vulnerability referenced in the following CVE:

  - In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow. (CVE-2026-86139)

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

  - In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow. (CVE-2026-86139)

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

ID	Name	Product	Family	Type	Severity
375009	Photon OS 5.0: Libxml2 PHSA-2026-5.0-91-1002	Nessus	PhotonOS Local Security Checks	Local	high
374971	Photon OS 5.0: Libxml2 PHSA-2026-5.0-92-1002	Nessus	PhotonOS Local Security Checks	Local	high
374269	Nessus Network Monitor < 6.6.0 Multiple Vulnerabilities (TNS-2026-32)	Nessus	Misc.	Local	high
365375	Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : libxml2 vulnerabilities (USN-8910-1)	Nessus	Ubuntu Local Security Checks	Local	high
464887	Echo: libxml2-2.15.3: security update to 2.15.3+e1	Tenable Cloud Security	Echo Local Security Checks	Local	high
464887	Echo: libxml2-2.15.3: security update to 2.15.3+e1	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	high
343108	Linux Distros Unpatched Vulnerability : CVE-2026-86139	Nessus	Misc.	Local	high

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CVE-2026-86139

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