CVE-2026-33079
In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in that allows an attacker who can supply Markdown…
Published May 6, 2026 · corrected/updated Aug 28, 2026 · evidence confidence medium
In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in that allows an attacker who can supply Markdown for parsing to cause denial of service. The regular expression used for parsing link titles contains overlapping alternatives that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a backslash followed by punctuation can be matched either as an escaped punctuation sequence or as two ordinary characters, creating an ambiguous pattern inside a repeated group. If an attacker supplies Markdown containing repeated ! sequences with no closing quote, the regex engine explores an exponential number of backtracking paths. This is reachable through normal Markdown parsing of inline links and block link reference definitions. A small crafted input can therefore cause significant CPU consumption and make applications using Mistune unresponsive.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-33079 is a high public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected version ranges have not been ingested yet. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 8.7. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-1333. Sources contributing to this record: cve_org, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
May 6, 2026 · NIST NVD
Detected
In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in that allows an attacker who can supply Markdown for parsing to cause denial of service. The regular expression used for parsing link titles contains overlapping alternatives that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a backsla
Aug 28, 2026 · NIST NVD
Updated
In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in that allows an attacker who can supply Markdown for parsing to cause denial of service. The regular expression used for parsing link titles contains overlapping alternatives that can trigger catastrophic backtracking. In both the double-quoted and single-quoted branches, a backsla
Sources
- CVE.orgVulnerability recordCVE-2026-33079
Official CVE identifier
cve.org - NIST NVDVulnerability recordCVE-2026-33079
In versions 3.0.0a1 through 3.2.0 of Mistune, there is a ReDoS (Regular Expression Denial of Service) vulnerability in that allows an attacker who can supply Markdown for parsing to cause denial of service. The regular expression used for parsing link titles conta
nvd.nist.gov