What is CVE-2026-118694?

CVE-2026-118694 is a high-severity vulnerability in Trentm Python-Markdown2, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-10-28.

How severe is CVE-2026-118694?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Trentm Python-Markdown2

CVE-2026-118694

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.

Published 2026-10-28.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Trentm Python-Markdown2

Weakness classification (CWE)

CWE-407 — Inefficient Algorithmic Complexity

References

github.com/trentm/python-markdown2/issues/750 (issue-tracking)
github.com/trentm/python-markdown2 (product)
github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py (technical-description)
github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py (technical-description)
github.com/trentm/python-markdown2/pull/751 (issue-tracking, patch)
www.vulncheck.com/advisories/python-markdown2-through-2.5.5-denial-of-service-v… (third-party-advisory)

Frequently asked questions

What is CVE-2026-118694?: CVE-2026-118694 is a high-severity vulnerability in Trentm Python-Markdown2, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-10-28.
How severe is CVE-2026-118694?: High severity. CVSS v3 base score is 7.5 out of 10.