anonhaven

CVE-2026-118694

HIGH CVSS 4.0: 8.7
Updated Oct 29, 2026
Python
Parameter Value
CVSS 8.7 (HIGH)
Type CWE-407
Vendor Python
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service

CVSS Vector v4.0

Weakness Type (CWE)

CWE-407

References 6

https://github.com/trentm/python-markdown2
disclosure@vulncheck.com
https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L1478-L1…
disclosure@vulncheck.com
https://github.com/trentm/python-markdown2/blob/2.5.5/lib/markdown2.py#L3029
disclosure@vulncheck.com
https://github.com/trentm/python-markdown2/issues/750
disclosure@vulncheck.com
https://github.com/trentm/python-markdown2/pull/751
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/python-markdown2-through-2.5.5-denial-of-s…
disclosure@vulncheck.com
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