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.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-407

Published

2026-10-28

Modified

2026-10-28

Record from

the NVD, synced 2026-10-28

References

• https://github.com/trentm/python-markdown2
• https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L1478-L1492
• https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L3029
• https://github.com/trentm/python-markdown2/issues/750
• https://github.com/trentm/python-markdown2/pull/751

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