CVE-2026-49851: lepture mistune · Uncontrolled Resource Consumption
Affects lepture mistuneSource CVE Database V5
Not known to be exploited · CVSS 8.7 High : upgrade to 3.3.0 soon.
Data as of 6 Nov 2026, 23:24 UTC
- 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:NExploitation evidence
Disclosed: evidence found.
CVE published 24 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| lepturemistune | Affected
| Fixed in
|
PyPImistunepkg:pypi/mistuneOther threats | Affected
| Fixed in
|
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
- github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-49851 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2492304 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:60520 (opens in a new tab)