Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk. When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error. A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong.

Multiple Vulnerabilities in Perl

An update of the perl package has been released.

The remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:22847-1 advisory.

    - CVE-2025-15649: `IO:Uncompress:Unzip` propagates uncaught exception when parsing zip header with     malformed DOS date       (bsc#1266361).
    - CVE-2026-8376: heap buffer overflow when compiling regular expressions with a repeated fixed string on     32-bit builds       (bsc#1266304).
    - CVE-2026-12087: `Socket`'s `pack_ip_mreq_source()` can copy adjacent heap memory into the returned     packed structure       (bsc#1268349).
    - CVE-2026-57432: an integer overflow in `S_measure_struct` leads to an out-of-bounds heap read in `pack`     and `unpack`       (bsc#1271372).
    - CVE-2026-13221: regex trie branch-count overflow leads to silent false-positive/negative pattern     matching       (bsc#1271386).

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-2026:21411-1 advisory.

    - CVE-2025-15649: `IO:Uncompress:Unzip` propagates uncaught exception when parsing zip header with     malformed DOS date       (bsc#1266361).
    - CVE-2026-8376: heap buffer overflow when compiling regular expressions with a repeated fixed string on     32-bit builds       (bsc#1266304).
    - CVE-2026-12087: `Socket`'s `pack_ip_mreq_source()` can copy adjacent heap memory into the returned     packed structure       (bsc#1268349).
    - CVE-2026-57432: an integer overflow in `S_measure_struct` leads to an out-of-bounds heap read in `pack`     and `unpack`       (bsc#1271372).
    - CVE-2026-13221: regex trie branch-count overflow leads to silent false-positive/negative pattern     matching       (bsc#1271386).

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

  - Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of     more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk. When such branches are     combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field.
    A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no     warning or error. A pattern of this shape produces false positive matches (matching strings it should not)     and false negative matches (failing to match strings it should). When such a pattern gates an access or     filtering decision, the result is wrong. (CVE-2026-13221)

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

ID	Name	Product	Family	Type	Severity
333513	Photon OS 5.0: Perl PHSA-2026-5.0-92-0946	Nessus	PhotonOS Local Security Checks	Local	critical
330290	SUSE SLES16 Security Update : perl (SUSE-SU-2026:22847-1)	Nessus	SuSE Local Security Checks	Local	critical
329512	openSUSE 16 Security Update : perl (openSUSE-SU-2026:21411-1)	Nessus	SuSE Local Security Checks	Local	critical
326561	Linux Distros Unpatched Vulnerability : CVE-2026-13221	Nessus	Misc.	Local	critical

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