CVE-2026-1323: The extension fails to properly define allowed classes used when deserializing transport failure metadata

Routine

HIGH 8.8UPGRADE

CVE-2026-1323 is a high-severity flaw (CVSS 8.8) affecting mailqueue. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The extension fails to properly define allowed classes used when deserializing transport failure metadata. An attacker may exploit this to execute untrusted serialized code. Note that an active exploit requires write access to the directory configured at $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_spool_filepath'].

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-502
Published	2026-03-17
Last modified	2026-06-17

Publisher (CNA): TYPO3 · Vendor: cps-it

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

Am I affected?

Timeline

2026-03-17 09:16 UTCPublished CVE record published
2026-06-17 10:15 UTCUpdated Record last modified

cps-it mailqueue UPGRADE

Affected: < 0.4.5 · >= 0.5.0 and < 0.5.2

Fixed in: 0.4.5, 0.5.2

Safe to downgrade to: a release before 0.5.0

1. Check installed version

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

2. UPGRADE to 0.4.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mailqueue

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 0.5.0 (Debian / Ubuntu)

apt-cache madison mailqueue sudo apt install mailqueue=<VERSION_BEFORE_0.5.0> sudo apt-mark hold mailqueue

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

dnf --showduplicates list mailqueue sudo dnf downgrade mailqueue-<VERSION_BEFORE_0.5.0> sudo dnf versionlock add mailqueue

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-2026-1323?

mailqueue: upgrade to 0.4.5, 0.5.2. Exact commands for each OS are on this page.

Is CVE-2026-1323 being exploited?

CVE-2026-1323 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-2026-1323 affect?

CVE-2026-1323 affects mailqueue. Severity is high (CVSS 8.8). The extension fails to properly define allowed classes used when deserializing transport failure metadata. An attacker may exploit this to execute untrusted serialized code. Note that an active exploit requires write access to the directory

How urgent is CVE-2026-1323?

Priority 34/100. High severity

Software pages

TYPO3 vulnerabilities

References

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