CVE-2021-28042: Deutsche Post Mailoptimizer 4.3 before 2020-11-09 allows Directory Traversal via a crafted ZIP archive to the

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HIGH 7.8DOWNGRADE

CVE-2021-28042 is a high-severity flaw (CVSS 7.8) affecting mailoptimizer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Deutsche Post Mailoptimizer 4.3 before 2020-11-09 allows Directory Traversal via a crafted ZIP archive to the Upload feature or the MO Connect component. This can lead to remote code execution.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	3.4% (top 11%)
CISA exploited list	No
Weakness	CWE-22
Published	2021-03-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: deutschepost

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

Am I affected?

Timeline

2021-03-05 22:15 UTCPublished CVE record published
2026-06-17 03:45 UTCUpdated Record last modified

deutschepost mailoptimizer DOWNGRADE

Affected: 4.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.3 (Debian / Ubuntu)

apt-cache madison mailoptimizer sudo apt install mailoptimizer=<VERSION_BEFORE_4.3> sudo apt-mark hold mailoptimizer

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mailoptimizer sudo dnf downgrade mailoptimizer-<VERSION_BEFORE_4.3> sudo dnf versionlock add mailoptimizer

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-2021-28042?

mailoptimizer: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-28042 being exploited?

CVE-2021-28042 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-2021-28042 affect?

CVE-2021-28042 affects mailoptimizer. Severity is high (CVSS 7.8). Deutsche Post Mailoptimizer 4.3 before 2020-11-09 allows Directory Traversal via a crafted ZIP archive to the Upload feature or the MO Connect component. This can lead to remote code execution.

How urgent is CVE-2021-28042?

Priority 50/100. High severity

References

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