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HIGH severity

CVE-2026-118694 — Trentm

HIGHFix: trentm/python-markdown2#751

CVE-2026-118694 is a high-severity (CVSS 7.5) CWE-407 vulnerability. No vendor fix is recorded yet; mitigation options are listed below.

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers…

Published
Updated
Affected
—
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 28, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Description

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2026-118694 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.
O3 Security · Impact-Aware SCA

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CVE-2026-118694: Trentm (High 7.5)