Vulnerability · Published Oct 30, 2026 · Assigned by CPANSec
CVE-2026-115866Starlet versions from 0.20 before 0.33 for Perl allow CPU exhaustion via regular expression backtracking when decoding chunked request bodies
Unrated
In plain English
A regular-expression denial of service in Starlet. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | starlet | no fix listed | DEBIAN-CVE-2026-115866 |
| Debian:13 | starlet | no fix listed | DEBIAN-CVE-2026-115866 |
| Debian:14 | starlet | 0.33-1 | DEBIAN-CVE-2026-115866 |
| Ubuntu:22.04:LTS | starlet | no fix listed | UBUNTU-CVE-2026-115866 |
| Ubuntu:24.04:LTS | starlet | no fix listed | UBUNTU-CVE-2026-115866 |
| Ubuntu:26.04:LTS | starlet | no fix listed | UBUNTU-CVE-2026-115866 |
| Ubuntu:26.10 | starlet | no fix listed | UBUNTU-CVE-2026-115866 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Starlet | 0.20 – before 0.33 |
Weakness: CWE-1333