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CVE-2026-49851

HIGH
8.7
CVSS 4.0
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.

Metadata

CVE ID
CVE-2026-49851
State
PUBLISHED
Assigner
GitHub_M
Reserved
2026-06-01 22:03 UTC
Published
2026-06-24 17:05 UTC
Last updated
2026-06-24 17:05 UTC
Primary CWE
CWE-400
CWE-400: Uncontrolled Resource Consumption
Vendor / Product
lepture / mistune
Sources
cve.org  ·  NVD

Severity & Metrics

8.7 HIGH CVSS 4.0
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
Affected products (1)
VendorProductPlatformVersions
lepture mistune — < 3.3.0
Weakness (CWE)
CWESourceDescription
CWE-400 cna CWE-400: Uncontrolled Resource Consumption
CWE-407 cna CWE-407: Inefficient Algorithmic Complexity
CWE-770 cna CWE-770: Allocation of Resources Without Limits or Throttling
CVSS scores (1)
ScoreSeverityVersionSourceVector
8.7 HIGH 4.0 cna 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
References (1)
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