CVE-2026-115866: high-severity vulnerability in Starlet
Starlet versions from 0.20 before 0.33 for Perl allow CPU exhaustion via regular expression backtracking when decoding chunked request bodies
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.2%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
StarletRelated CVEs — Starlet
In the same product, most dangerous first.
CVE-2026-116128HIGHStarlet versions from 0.20 before 0.33 for Perl allow memory exhaustion via unbounded buffering when decoding chunked request bodiesEPSS 0.2%CVE-2026-115865HIGHStarlet versions before 0.33 for Perl allow a request declaring a large Content-Length to kill a worker by exhausting memoryEPSS 0.2%CVE-2026-116127CRITICALStarlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a persistent or pipelined connectionEPSS 0.2%