markdown-it: Quadratic-time rendering of a single multi-line link reference definition with default options (regression since 14.0)
markdown-it is a Markdown parser. From versions 14.1.0 to before 14.3.3, and 15.0.0 to before 15.0.3, a link reference definition whose label or title is never closed is O(n²) with default options. Continuation lines are pulled lazily with str += lineContent in src/rules_block/reference.ts, and the subsequent charCodeAt and slice calls flatten the V8 cons-string, copying everything collected so far; this runs before the rule decides the definition is invalid. No options are required to trigger it. This issue has been patched in versions 14.3.3 and 15.0.3.
markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled
markdown-it is a Markdown parser. Prior to 14.3.3 and 15.0.3, when the html option or commonmark preset is enabled and the constructs occur inside a paragraph, attacker-controlled Markdown containing repeated unterminated inline HTML comments, processing instructions, declarations, or CDATA sections reaches src/rules_inline/html_inline.ts. Its HTML_TAG_RE match searches the remaining suffix for the appropriate terminator; when no terminator is present, parsing advances to the next opener and repeats the match over overlapping input, causing quadratic processing and denial of service through event-loop blocking or an unresponsive browser main
markdown-it: Quadratic complexity in smartquotes with unmatched closing quotes
markdown-it is a Markdown parser. Prior to 14.3.2 and 15.0.2, when typographer: true is enabled, specially crafted Markdown can cause quadratic processing time in the smartquotes rule, potentially leading to denial of service in applications processing untrusted input. Many opening double quotes followed by unmatched closing single quotes cause repeated scans of the entire opener stack. The same issue occurs with the quote types reversed. The default configuration (typographer: false) is not affected, but this option is enabled with high probability. This issue is fixed in versions 14.3.2 and 15.0.2.
markdown-it linkify: true has two quadratic paths, so a few hundred KB of markdown blocks the event loop for tens of seconds
## Summary
Two independent quadratic paths in the `linkify: true` handling. Both are in markdown-it's own code rather than in linkify-it, which stays linear on both payloads.
`src/rules_core/linkify.ts` calls `arrayReplaceAt` once per linkified text token, and that rebuilds the whole `children` array each time. A paragraph of N soft-broken lines is one inline token with about 2N children, so you get N rebuilds over a 2N array. Schema-less emails are what reach it. A `http://` link gets consumed by the inline rule first and never arrives as a text token, so those stay linear.
`src/rules_inline/linkify.ts` runs `state.pending.match(SCHEME_RE
markdown-it: Quadratic complexity DoS in smartquotes rule via replaceAt string operations
markdown-it is a Markdown parser. Versions 14.1.1 and below contain a denial-of-service vulnerability when typographer: true is enabled, due to quadratic (O(n^2)) processing in the smartquotes rule. The issue stems from repeatedly modifying strings with replaceAt(), which performs O(n) slicing and concatenation per quote character. This can cause excessive CPU consumption when parsing quote-heavy, user-supplied markdown and may let attackers degrade or disrupt service availability. Although typographer is disabled by default, many production apps enable it for smart typography, making the issue relevant. This issue has been fixed in version 1
Versions of the package markdown-it from 13.0.0 and before 14.1.1 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the use of the regex /\*+$/ in the linkify function. An attacker can supply a long sequence of * characters followed by a non-matching character, which triggers excessive backtracking and may lead to a denial-of-service condition.
A vulnerability was found in markdown-it up to 2.x. It has been classified as problematic. Affected is an unknown function of the file lib/common/html_re.js. The manipulation leads to inefficient regular expression complexity. Upgrading to version 3.0.0 is able to address this issue. The name of the patch is 89c8620157d6e38f9872811620d25138fc9d1b0d. It is recommended to upgrade the affected component. The identifier of this vulnerability is VDB-216852.
markdown-it is a Markdown parser. Prior to version 1.3.2, special patterns with length greater than 50 thousand characterss could slow down the parser significantly. Users should upgrade to version 12.3.2 to receive a patch. There are no known workarounds aside from upgrading.