Mistune before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parse_link_text that allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward scans that stall worker processes for minutes.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3386 advisory.

    Mistune before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parse_link_text that     allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can     submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward     scans that stall worker processes for minutes. (CVE-2026-115347)

    Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that     allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters.
    Attackers can send small markdown payloads that trigger O(N^2) parse_link_text and parse_link_label     probing, occupying rendering workers for 30+ seconds per 16 KB input. (CVE-2026-115352)

Tenable has extracted the preceding description block directly from the tested product 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-ea39a303cf advisory.

    Update to 3.3.4


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-2026-340793a2f1 advisory.

    Update to 3.3.4

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

  - Mistune before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parse_link_text that     allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can     submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward     scans that stall worker processes for minutes. (CVE-2026-115347)

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

ID	Name	Product	Family	Type	Severity
377958	Amazon Linux 2023 : python3-mistune (ALAS2023-2026-3386)	Nessus	Amazon Linux Local Security Checks	Local	high
376834	Fedora 44 : python-mistune (2026-ea39a303cf)	Nessus	Fedora Local Security Checks	Local	critical
376819	Fedora 43 : python-mistune (2026-340793a2f1)	Nessus	Fedora Local Security Checks	Local	critical
371291	Linux Distros Unpatched Vulnerability : CVE-2026-115347	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-115347

high

Tenable Plugins

high

critical

critical

high