CVE-2026-40560: Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman

Q: How do I fix CVE-2026-40560?

starman: upgrade to 0.4018. Exact commands for each OS are on this page.

Q: Is CVE-2026-40560 being exploited?

CVE-2026-40560 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40560 affect?

CVE-2026-40560 affects starman. Severity is high (CVSS 7.5). Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per

Q: How urgent is CVE-2026-40560?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-40560 is a high-severity flaw (CVSS 7.5) affecting starman. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman 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.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-444
Published	2026-04-29
Last modified	2026-07-24

Publisher (CNA): CPANSec · Vendor: miyagawa

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-29 00:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

miyagawa starman UPGRADE

Affected: < 0.4018

Fixed in: 0.4018

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy starman || rpm -q starman || starman --version

2. UPGRADE to 0.4018 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade starman

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade starman

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40560?

starman: upgrade to 0.4018. Exact commands for each OS are on this page.

Is CVE-2026-40560 being exploited?

CVE-2026-40560 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40560 affect?

CVE-2026-40560 affects starman. Severity is high (CVSS 7.5). Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per

How urgent is CVE-2026-40560?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

References

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