CVE-2026-118694

high

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.

References

https://www.vulncheck.com/advisories/python-markdown2-through-2.5.5-denial-of-service-via-unclosed-inline-link-destinations

https://github.com/trentm/python-markdown2/pull/751

https://github.com/trentm/python-markdown2/issues/750

https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L3029

https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L1478-L1492

https://github.com/trentm/python-markdown2

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-112495

Details

Source: Mitre, NVD

Published: 2026-10-28

Updated: 2026-10-29

Risk Information

CVSS v2

Base Score: 7.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

Severity: High

CVSS v3

Base Score: 7.5

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

Severity: High

CVSS v4

Base Score: 8.7

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

Severity: High

EPSS

EPSS: 0.00453