🛡️ CVE-2026-40561 — starlet

🟡 CVSS 5.3 — Medium ✅ No Known Exploit CWE-444 NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence.

Starlet incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per RFC 7230 3.3.3, Transfer-Encoding must take precedence.

An attacker could exploit this to smuggle malicious HTTP requests via a front-end reverse proxy.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

Weakness class

CVE-2026-40561 is classified as CWE-444: HTTP Request Smuggling. A proxy and a server disagree on where one request ends, letting an attacker slip a second request past the front end.

Affected software

CVE-2026-40561 is recorded against 1 package.

  • starlet (fixed in 0.31)

Timeline and source

Published on 3 May 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

datatracker.ietf.org
github.com
metacpan.org
www.openwall.com

CVE-2026-40561 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE CWE-444
Public Exploit ✅ No
Source NVD
Published 2026-05-03
Updated 2026-08-11
Modified 2026-06-17

Affected Packages

Software From version Fixed in
starlet — 0.31

Vulnerability Monitoring

Track new vulnerabilities in starlet

CVE-2026-40561 is rated CVSS 5.3 Medium. BotEraser monitors your WordPress installation and notifies you when software you use appears in our vulnerability database.

Set Up Free Alerts →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.