Pulldown cmark: Exponential event growth with `ENABLE_WIKILINKS`
Affects pulldown-cmarkSource GCVE Database
CVSS 7.5 High : upgrade to 0.13.5 soon.
Data as of 28 Oct 2026, 09:13 UTC
- Patch
- Available – fixed in 0.13.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HWhat to do
Upgrade pulldown-cmark to 0.13.5.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
crates.iopulldown-cmarkpkg:cargo/pulldown-cmarkOther threats | Affected
| Fixed in
|
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Description
When `Options::ENABLE_WIKILINKS` is enabled, a wikilink with a pipe separator and empty display text, such as `[[a|]]`, leaks its child node's sibling chain into the content that follows it. Each such link roughly doubles the number of events the parser yields for the rest of the document, so output grows exponentially with input size: 16 repetitions of `[[a|]] ` (112 bytes) yield 327,676 events, where the fixed parser yields 65. A document of a few kilobytes is enough to exhaust memory in a process that collects the events or renders them to HTML. Applications that parse untrusted Markdown with `ENABLE_WIKILINKS` set, including through `Options::all()`, are affected. The option is off by default. Parsing without it is not affected. The flaw was fixed in [#1102](https://github.com/pulldown-cmark/pulldown-cmark/pull/1102) and released in 0.13.5.