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VulnerabilityPublished Updated

Pulldown cmark: Exponential event growth with `ENABLE_WIKILINKS`

Affects pulldown-cmarkSource GCVE Database

0

CVSS 7.5 High : upgrade to 0.13.5 soon.

Data as of 28 Oct 2026, 09:13 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
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:H

What to do

Upgrade pulldown-cmark to 0.13.5.

Affected software

ProductAffectedFixed in
crates.iopulldown-cmarkpkg:cargo/pulldown-cmarkOther threatsAffected
  • >=0.13.0 <0.13.5
Fixed in
  • 0.13.5

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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.

References

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