CVE-2026-115349

Mistune 3.0.0 before 3.3.0 Denial of Service via Nested Bracket Parsing

Published Oct 22, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Description
Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity denial of service vulnerability in the parse_link_text function in src/mistune/helpers.py. Attackers can submit markdown with deeply nested square brackets triggering quadratic parsing time, exhausting server CPU with small crafted requests.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Lepture
Lepture mistune
Vendors & Products Lepture
Lepture mistune
Type Values Removed Values Added
Description Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity denial of service vulnerability in the parse_link_text function in src/mistune/helpers.py. Attackers can submit markdown with deeply nested square brackets triggering quadratic parsing time, exhausting server CPU with small crafted requests.
Title Mistune 3.0.0 before 3.3.0 Denial of Service via Nested Bracket Parsing
First Time appeared Mistune Project
Mistune Project mistune
Weaknesses CWE-1333
CWE-606
CPEs cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*
Vendors & Products Mistune Project
Mistune Project mistune
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'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'}

threat_severity

Important

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Oct 26, 2026, 7:38 PM
Reserved
Oct 22, 2026, 11:20 AM
Status
Deferred
Published
Oct 22, 2026, 7:17 PM
Modified
Oct 26, 2026, 8:17 PM
Severity
Important
Public date
Oct 22, 2026, 7:13 PM