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VulnerabilityPublished Updated

CVE-2026-49851: lepture mistune · Uncontrolled Resource Consumption

Affects lepture mistuneSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 3.3.0 soon.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.3.0
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

What to do

Upgrade lepture mistune to 3.3.0.

Affected software

ProductAffectedFixed in
lepturemistuneAffected
  • <3.3.0
Fixed in
  • 3.3.0
PyPImistunepkg:pypi/mistuneOther threatsAffected
  • <3.3.0
Fixed in
  • 3.3.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Mistune version 3.3.0. Users should upgrade to version 3.3.0 or later to remediate this vulnerability. Patch status is confirmed by the vendor advisory. No additional mitigation steps are indicated.

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.

References

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