CVE-2026-65906: In JetBrains TeamCity before 2026.1.2, 2025.11.6 сode execution via Kotlin DSL sandbox escape was possible

This month

HIGH 8.8UPGRADE

CVE-2026-65906 is a high-severity flaw (CVSS 8.8) affecting teamcity. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In JetBrains TeamCity before 2026.1.2, 2025.11.6 сode execution via Kotlin DSL sandbox escape was possible

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	0.7% (top 49%)
CISA exploited list	No
Weakness	CWE-94
Published	2026-07-23
Last modified	2026-10-24

Publisher (CNA): JetBrains s.r.o. · Vendor: jetbrains

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-23 13:16 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

jetbrains teamcity UPGRADE

Affected: < 2025.11.6 · >= 2026.1 and < 2026.1.2

Fixed in: 2025.11.6, 2026.1.2

Safe to downgrade to: a release before 2026.1

1. Check installed version

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

2. UPGRADE to 2025.11.6 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade teamcity

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 2026.1 (Debian / Ubuntu)

apt-cache madison teamcity sudo apt install teamcity=<VERSION_BEFORE_2026.1> sudo apt-mark hold teamcity

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

dnf --showduplicates list teamcity sudo dnf downgrade teamcity-<VERSION_BEFORE_2026.1> sudo dnf versionlock add teamcity

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.

Exact fixes by distribution

Fedora 46 · gnome-shell-extension-tiling-assistant · FIXED · 56-1.fc46 · FEDORA-2026-ebf66a5321 · source

sudo dnf upgrade --advisory=FEDORA-2026-ebf66a5321

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-2026-65906?

teamcity: upgrade to 2025.11.6, 2026.1.2. Exact commands for each OS are on this page.

Is CVE-2026-65906 being exploited?

CVE-2026-65906 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-2026-65906 affect?

CVE-2026-65906 affects teamcity. Severity is high (CVSS 8.8). In JetBrains TeamCity before 2026.1.2, 2025.11.6 сode execution via Kotlin DSL sandbox escape was possible

How urgent is CVE-2026-65906?

Priority 44/100. High severity

Related CVEs

CVE-2026-63077 CRITICAL 9.8 EXPLOITED UPGRADE JetBrains TeamCity Deserialization of Untrusted Data Vulnerability

References

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