CVE-2026-115866

Description

Starlet versions from 0.20 before 0.33 for Perl allow CPU exhaustion via regular expression backtracking when decoding chunked request bodies. A chunk-size line is matched as a run of hex digits, then .* and a CRLF. A run followed by a bare LF and then a CRLF can never match, and the engine retries the match once for each digit, so the time taken grows with the square of the run length. Nothing limits the length of the run, which can span several reads. A remote attacker can occupy a worker for about a minute of CPU time with one 128 KiB request, before the application is called.

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Weakness Type (CWE)

CWE-1333 CWE-1333

References

Other References

https://github.com/kazuho/Starlet/commit/229ea56b3b50028e2a644156317e8d0e7cf68a1f.patch https://metacpan.org/release/KAZUHO/Starlet-0.33/changes

Frequently Asked Questions

What is CVE-2026-115866? +

Starlet versions from 0.20 before 0.33 for Perl allow CPU exhaustion via regular expression backtracking when decoding chunked request bodies. A chunk-size line is matched as a run of hex digits, then .* and a CRLF. A run followed by a bare LF and then a CRLF can never match, and the engine retries the match once for each digit, so the time taken grows with the square of the run length. Nothing limits the length of the run, which can span several reads. A remote attacker can occupy a worker for about a minute of CPU time with one 128 KiB request, before the application is called.

How do I check if I'm vulnerable to CVE-2026-115866? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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