NIXPKGS-2026-1980

GitHub issue published 6 hours ago

Mistune: Potential DoS via quadratic-time parsing in parse_link_text

Permalink CVE-2026-49851

8.7 HIGH

CVSS version (CVSS): 4.0
Attack Vector (AV): Network (N)
Attack Complexity (AC): Low (L)
Attack Requirement (AT): None (N)
Privileges Required (PR): None (N)
User Interaction (UI): None (N)
Vulnerable System Impact Confidentiality (VC): None (N)
Vulnerable System Impact Integrity (VI): None (N)
Vulnerable System Impact Availability (VA): High (H)
Subsequent System Impact Confidentiality (SC): None (N)
Subsequent System Impact Integrity (SI): None (N)
Subsequent System Impact Availability (SA): None (N)
Modified Attack Vector (MAV): Network (N)
Modified Attack Complexity (MAC): Low (L)
Modified Attack Requirement (MAT): None (N)
Modified Privileges Required (MPR): None (N)
Modified User Interaction (MUI): None (N)
Modified Vulnerable System Impact Confidentiality (MVC): None (N)
Modified Vulnerable System Impact Integrity (MVI): None (N)
Modified Vulnerable System Impact Availability (MVA): High (H)
Modified Subsequent System Impact Confidentiality (MSC): Negligible (N)
Modified Subsequent System Impact Integrity (MSI): Negligible (N)
Modified Subsequent System Impact Availability (MSA): Negligible (N)
Safety (S): Not Defined (X)
Automatable (AU): Not Defined (X)
Recovery (R): Not Defined (X)
Value Density (V): Not Defined (X)
Vulnerability Response Effort (RE): Not Defined (X)
Provider Urgency (U): Not Defined (X)
Confidentiality Req. (CR): Not Defined (X)
Integrity Req. (IR): Not Defined (X)
Availability Req. (AR): Not Defined (X)
Exploit Maturity (E): Not Defined (X)

updated 6 hours ago by @LeSuisse Activity log

Created suggestion 12 hours ago
@LeSuisse accepted 6 hours ago
@LeSuisse published on GitHub 6 hours ago

Mistune: Potential DoS via quadratic-time parsing in parse_link_text

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.