DEBIAN-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 `LINK_TITLE_RE` 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.
DEBIAN-CVE-2026-33079
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-33079
mistune
Source reference: /affected/0/package/name
- Affected versions
- 3.1.3-1
Source reference:
/affected/0/versions3.1.4-1Source reference:
/affected/0/versions3.3.4-1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
mistune
Source reference: /affected/1/package/name
- Affected versions
- 3.1.3-1
Source reference:
/affected/1/versions3.1.4-1Source reference:
/affected/1/versions3.3.4-1Source reference:
/affected/1/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "mistune",
"purl": "pkg:deb/debian/mistune?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"3.1.3-1",
"3.1.4-1",
"3.3.4-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33079.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "mistune",
"purl": "pkg:deb/debian/mistune?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"3.1.3-1",
"3.1.4-1",
"3.3.4-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33079.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #56755 · Revision 1
- Added to Heist Feed
- Publisher date