vulnerability / NVI-00017759 / Revision 1
LinkifyIt#match scan loop has quadratic algorithmic complexity
GitHub lists this reviewed advisory for linkify-it. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
linkify-it
source listed<= 5.0.0
## Summary `LinkifyIt.prototype.match` — the package's primary public API — has **O(N²) algorithmic complexity** for inputs containing many fuzzy links or emails. This is not a regex backtrack bug; it's a structural issue in the JS-level scan loop that re-slices the input and re-runs unanchored regex searches on progressively shorter tails, N times. 64 KB of `"a@b.com\n"` repeated burns ~2.5 s of single-threaded CPU; 128 KB takes ~10 s. Doubling the input quadruples the time — textbook O(N²). The same cost passes through `markdown-it` (`linkify:true`) unmodified. Any service that synchronously renders untrusted Markdown with linkify enabled on a request hot-path (forums, comments, chat, wikis, AI chat UIs) inherits a worker-process DoS triggerable by a tens-of-KB request body. ## Affected component - HEAD audited: `8e887d5bace3f5b09b1d1f70492fa0364ef1793d` (v5.0.0) - Vulnerable function: `LinkifyIt.prototype.match` — `index.mjs:528-554` - Re-scan call sites inside `test()`: `index.mjs:444` (fuzzy host search), `:448` (fuzzy link match), `:467` (fuzzy email match) - Transitive consumer: `markdown-it` (~21.6M weekly npm DLs) calls `linkify.match()` at `lib/rules_core/linkify.mjs
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-22p9-wv53-3rq4 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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