CVE-2025-40934: XML-Sig versions 0.27 through 0.67 for Perl incorrectly validates XML files if signatures are omitted. An att

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CRITICAL 9.3REMOTEUPGRADE

CVE-2025-40934 is a critical-severity flaw (CVSS 9.3) affecting \. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XML-Sig versions 0.27 through 0.67 for Perl incorrectly validates XML files if signatures are omitted. An attacker can remove the signature from the XML document to make it pass the verification check. XML-Sig is a Perl module to validate signatures on XML files. An unsigned XML file should return an error message. The affected versions return true when attempting to validate an XML file that contains no signatures.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.3 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 93%)
CISA exploited list	No
Weakness	CWE-347
Published	2025-11-26
Last modified	2026-10-18

Publisher (CNA): CPANSec · Vendor: xml\

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-11-26 23:15 UTCPublished CVE record published
2026-10-18 20:10 UTCUpdated Record last modified

xml\ \ UPGRADE

Affected: >= 0.27 and <= 0.67

Fixed in: newer than 0.67

Safe to downgrade to: a release before 0.27

1. Check installed version

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

2. UPGRADE to newer than 0.67 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade

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 0.27 (Debian / Ubuntu)

apt-cache madison sudo apt install =<VERSION_BEFORE_0.27> sudo apt-mark hold

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

dnf --showduplicates list sudo dnf downgrade -<VERSION_BEFORE_0.27> sudo dnf versionlock add

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-2025-40934?

\: upgrade to newer than 0.67. Exact commands for each OS are on this page.

Is CVE-2025-40934 being exploited?

CVE-2025-40934 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-2025-40934 affect?

CVE-2025-40934 affects \. Severity is critical (CVSS 9.3). XML-Sig versions 0.27 through 0.67 for Perl incorrectly validates XML files if signatures are omitted. An attacker can remove the signature from the XML document to make it pass the verification check. XML-Sig is a Perl module to validate

How urgent is CVE-2025-40934?

Priority 39/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

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References

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