CVE-2025-40907: FCGI versions 0.44 through 0.82, for Perl, include a vulnerable version of the FastCGI fcgi2 (aka fcgi) librar

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MEDIUM 5.3REMOTEUPGRADE

CVE-2025-40907 is a medium-severity flaw (CVSS 5.3) affecting fcgi. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FCGI versions 0.44 through 0.82, for Perl, include a vulnerable version of the FastCGI fcgi2 (aka fcgi) library. The included FastCGI library is affected by CVE-2025-23016, causing an integer overflow (and resultant heap-based buffer overflow) via crafted nameLen or valueLen values in data to the IPC socket. This occurs in ReadParams in fcgiapp.c.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-122, CWE-190
Published	2025-05-16
Last modified	2026-06-17

Publisher (CNA): CPANSec · Vendor: fastcgi

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-05-16 13:15 UTCPublished CVE record published
2026-06-17 09:22 UTCUpdated Record last modified

fastcgi fcgi UPGRADE

Affected: >= 0.44 and <= 0.82

Fixed in: newer than 0.82

Safe to downgrade to: a release before 0.44

1. Check installed version

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

2. UPGRADE to newer than 0.82 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fcgi

Note

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

3. If no update is available yet, DOWNGRADE to a release before 0.44 (Debian / Ubuntu)

apt-cache madison fcgi sudo apt install fcgi=<VERSION_BEFORE_0.44> sudo apt-mark hold fcgi

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list fcgi sudo dnf downgrade fcgi-<VERSION_BEFORE_0.44> sudo dnf versionlock add fcgi

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2025-40907?

fcgi: upgrade to newer than 0.82. Exact commands for each OS are on this page.

Is CVE-2025-40907 being exploited?

CVE-2025-40907 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-2025-40907 affect?

CVE-2025-40907 affects fcgi. Severity is medium (CVSS 5.3). FCGI versions 0.44 through 0.82, for Perl, include a vulnerable version of the FastCGI fcgi2 (aka fcgi) library. The included FastCGI library is affected by CVE-2025-23016, causing an integer overflow (and resultant heap-based buffer over

How urgent is CVE-2025-40907?

Priority 42/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

References

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