In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in `LINK_TITLE_RE` that allows an attacker who can supply Markdown for parsing to cause denial of service. The regular expression used for parsing link titles contains overlapping alternatives that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a backslash followed by punctuation can be matched either as an escaped punctuation sequence or as two ordinary characters, creating an ambiguous pattern inside a repeated group. If an attacker supplies Markdown containing repeated ! sequences with no closing quote, the regex engine explores an exponential number of backtracking paths. This is reachable through normal Markdown parsing of inline links and block link reference definitions. A small crafted input can therefore cause significant CPU consumption and make applications using Mistune unresponsive.

An update of the python3 package has been released.

The remote SUSE Linux SLES16 / SLES_SAP16 host has a package installed that is affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:21858-1 advisory.

    This update for python-mistune fixes the following issues

    - CVE-2026-33079: ReDoS in `LINK_TITLE_RE` can lead to denial of service via a crafted Markdown     (bsc#1264347).
    - CVE-2026-33441: processing of malformed reference links can lead to excessive resource consumption and     denial of       service (bsc#1264752).
    - CVE-2026-44708: improper HTML escaping in the math plugin can lead to XSS (bsc#1264751).
    - CVE-2026-44896: improper escaping in `render_figure` can lead to attribute injection and XSS     (bsc#1264754).
    - CVE-2026-44897: improper sanitization of user-controlled input in `HTMLRenderer.heading` can lead to XSS       (bsc#1264750).
    - CVE-2026-44898: improper sanitization of user-supplied HTML input in `render_toc_ul` can lead to XSS     (bsc#1265052).
    - CVE-2026-44899: improper input verification in Image directive plugin and improper escaping in     `render_block_image`       can lead to CSS injection (bsc#1265053).

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 a package installed that is affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:20827-1 advisory.

    This update for python-mistune fixes the following issues

    - CVE-2026-33079: ReDoS in `LINK_TITLE_RE` can lead to denial of service via a crafted Markdown     (bsc#1264347).
    - CVE-2026-33441: processing of malformed reference links can lead to excessive resource consumption and     denial of       service (bsc#1264752).
    - CVE-2026-44708: improper HTML escaping in the math plugin can lead to XSS (bsc#1264751).
    - CVE-2026-44896: improper escaping in `render_figure` can lead to attribute injection and XSS     (bsc#1264754).
    - CVE-2026-44897: improper sanitization of user-controlled input in `HTMLRenderer.heading` can lead to XSS       (bsc#1264750).
    - CVE-2026-44898: improper sanitization of user-supplied HTML input in `render_toc_ul` can lead to XSS     (bsc#1265052).
    - CVE-2026-44899: improper input verification in Image directive plugin and improper escaping in     `render_block_image`       can lead to CSS injection (bsc#1265053).

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.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service)
    vulnerability in `LINK_TITLE_RE` that allows an attacker who can supply Markdown for parsing to cause
    denial of service. The regular expression used for parsing link titles contains overlapping alternatives
    that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a
    backslash followed by punctuation can be matched either as an escaped punctuation sequence or as two
    ordinary characters, creating an ambiguous pattern inside a repeated group. If an attacker supplies
    Markdown containing repeated ! sequences with no closing quote, the regex engine explores an exponential
    number of backtracking paths. This is reachable through normal Markdown parsing of inline links and block
    link reference definitions. A small crafted input can therefore cause significant CPU consumption and make
    applications using Mistune unresponsive. (CVE-2026-33079)

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

  - In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service)     vulnerability in `LINK_TITLE_RE` that allows an attacker who can supply Markdown for parsing to cause     denial of service. The regular expression used for parsing link titles contains overlapping alternatives     that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a     backslash followed by punctuation can be matched either as an escaped punctuation sequence or as two     ordinary characters, creating an ambiguous pattern inside a repeated group. If an attacker supplies     Markdown containing repeated ! sequences with no closing quote, the regex engine explores an exponential     number of backtracking paths. This is reachable through normal Markdown parsing of inline links and block     link reference definitions. A small crafted input can therefore cause significant CPU consumption and make     applications using Mistune unresponsive. (CVE-2026-33079)

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

ID	Name	Product	Family	Type	Severity
334049	Photon OS 5.0: Python3 PHSA-2026-5.0-92-0882	Nessus	PhotonOS Local Security Checks	Local	high
321579	Photon OS 5.0: Python3 PHSA-2026-5.0-0882	Nessus	PhotonOS Local Security Checks	Local	high
318185	SUSE SLES16 Security Update : python-mistune (SUSE-SU-2026:21858-1)	Nessus	SuSE Local Security Checks	Local	high
318089	openSUSE 16 Security Update : python-mistune (openSUSE-SU-2026:20827-1)	Nessus	SuSE Local Security Checks	Local	high
441324	SCA: security update for mistune (GHSA-8mp2-v27r-99xp)	Tenable Cloud Security	SCA Checks	Local	high
441324	SCA: security update for mistune (GHSA-8mp2-v27r-99xp)	Tenable Self-Hosted Container Security	SCA Checks	Local	high
313071	Linux Distros Unpatched Vulnerability : CVE-2026-33079	Nessus	Misc.	Local	high

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