Exponential event growth with `ENABLE_WIKILINKS`

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

18 Oct 2026 12:00:00 UTC

Source modified

28 Oct 2026 09:00:02 UTC

Observed here

28 Oct 2026 10:33:29 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H