Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| lepture / mistune | affected >=3.0.0a1, <= 3.2.0 |
CWE
CWE-1333
References
- https://github.com/lepture/mistune/security/advisories/GHSA-8mp2-v27r-99xp
- https://github.com/lepture/mistune/blob/df23edd60b43b639d2e6760ef9dd3d618aa11c21/src/mistune/helpers.py#L20-L25
ADP enrichment
No English description supplied.
A flaw was found in Mistune, a Markdown parser. This vulnerability, known as Regular Expression Denial of Service (ReDoS), exists in the `LINK_TITLE_RE` regular expression. A remote attacker can exploit this by providing specially crafted Markdown input, which causes the regular expression engine to engage in catastrophic backtracking. This leads to significant CPU consumption, making applications that use Mistune unresponsive and resulting in a Denial of Service.