Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.

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.

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

  - Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading()     builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML  with     no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character  in the     id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event     handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.
    (CVE-2026-44897)

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

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

  - Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading()
    builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with
    no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the
    id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event
    handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.
    (CVE-2026-44897)

ID	Name	Product	Family	Type	Severity
334706	Photon OS 5.0: Python3 PHSA-2026-5.0-92-0947	Nessus	PhotonOS Local Security Checks	Local	medium
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
317297	Linux Distros Unpatched Vulnerability : CVE-2026-44897	Nessus	Misc.	Local	medium
441569	SCA: security update for mistune (GHSA-v87v-83h2-53w7)	Tenable Cloud Security	SCA Checks	Local	medium
441569	SCA: security update for mistune (GHSA-v87v-83h2-53w7)	Tenable Self-Hosted Container Security	SCA Checks	Local	medium

Detections

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CVE-2026-44897

medium

Tenable Plugins

medium

high

high

medium

medium

medium