CVE-2026-34838: Group-Office is an enterprise customer relationship management and groupware tool

This month

CRITICAL 9.9UPGRADE

CVE-2026-34838 is a critical-severity flaw (CVSS 9.9) affecting group-office. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Group-Office is an enterprise customer relationship management and groupware tool. Prior to versions 6.8.156, 25.0.90, and 26.0.12, a vulnerability in the AbstractSettingsCollection model leads to insecure deserialization when these settings are loaded. By injecting a serialized FileCookieJar object into a setting string, an authenticated attacker can achieve Arbitrary File Write, leading directly to Remote Code Execution (RCE) on the server. Thi

Why this priority

Critical severity

A fixed release or distro patch exists.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-502
Published	2026-04-02
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: intermesh

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

Am I affected?

Timeline

2026-04-02 20:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

intermesh group-office UPGRADE

Affected: < 6.8.156 · >= 25.0.1 and < 25.0.90 · >= 26.0.1 and < 26.0.12

Fixed in: 6.8.156, 25.0.90, 26.0.12

Safe to downgrade to: a release before 25.0.1

1. Check installed version

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

2. UPGRADE to 6.8.156 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade group-office

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 25.0.1 (Debian / Ubuntu)

apt-cache madison group-office sudo apt install group-office=<VERSION_BEFORE_25.0.1> sudo apt-mark hold group-office

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

dnf --showduplicates list group-office sudo dnf downgrade group-office-<VERSION_BEFORE_25.0.1> sudo dnf versionlock add group-office

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-2026-34838?

group-office: upgrade to 6.8.156, 25.0.90, 26.0.12. Exact commands for each OS are on this page.

Is CVE-2026-34838 being exploited?

CVE-2026-34838 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-2026-34838 affect?

CVE-2026-34838 affects group-office. Severity is critical (CVSS 9.9). Group-Office is an enterprise customer relationship management and groupware tool. Prior to versions 6.8.156, 25.0.90, and 26.0.12, a vulnerability in the AbstractSettingsCollection model leads to insecure deserialization when these setting

How urgent is CVE-2026-34838?

Priority 51/100. Critical severity

Related CVEs

CVE-2026-33755 HIGH 8.8 UPGRADE Group-Office is an enterprise customer relationship management and groupware tool

References

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