⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 6.8

How to Fix CVE-2026-23626: Server-Side Template Injection in kimai

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 6.8 - Medium
Actively exploited?Not currently listed in CISA KEV
Affected< 2.46.0
Fixed inSee vendor advisory
Type (CWE)CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine

What is CVE-2026-23626?

CVE-2026-23626 is a server-side template injection flaw in kimai. User input is rendered as part of a template expression, which the engine then evaluates, giving the attacker code execution. Vendor description: Kimai is a web-based multi-user time-tracking application. Prior to version 2.46.0, Kimai's export functionality uses a Twig sandbox with an overly permissive security policy (DefaultPolicy) that allows arbitrary method calls on objects available in the template context.

Why this CVE matters

Server-side template injection is one of the cleanest paths from web request to code execution. The vulnerable parameter is usually attacker-controlled by design, which means proof-of-concept payloads are short and reliable.

For deployments of kimai that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open kimai's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-23626

  1. Read the vendor advisory in full: https://github.com/kimai/kimai/security/advisories/GHSA-jg2j-2w24-54cg
  2. Upgrade kimai to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Apply the vendor patch


# Target fixed version: see advisory (https://github.com/kimai/kimai/security/advisories/GHSA-jg2j-2w24-54cg)
# Source advisory: https://github.com/kimai/kimai/security/advisories/GHSA-jg2j-2w24-54cg
# Product: kimai (kimai)

# 1. Locate any installed build of kimai on the host.
dpkg -l 2>/dev/null | grep -i kimai
rpm -qa 2>/dev/null | grep -i kimai

# 2. The vendor does not publish through standard distro repos for most
#    products. Download the patched installer / package from the advisory URL:
#       https://github.com/kimai/kimai/security/advisories/GHSA-jg2j-2w24-54cg
#    Verify the signature or SHA-256 the vendor publishes alongside it.

# 3. Apply the vendor installer (example - adjust extension per platform).
#    .deb:    sudo dpkg -i kimai-<patched-version>.deb
#    .rpm:    sudo rpm -Uvh kimai-<patched-version>.rpm
#    .tar.gz: tar xzf kimai-<patched-version>.tar.gz && sudo ./install.sh

# 4. Restart the affected service so the patched binary loads.
sudo systemctl restart kimai 2>/dev/null || true

# 5. Confirm the running version matches the fixed version.
kimai --version 2>/dev/null || true


# Windows admin workstation - try winget first if the vendor publishes there.
winget search 'kimai'
winget upgrade --id 'kimai' --silent --accept-source-agreements --accept-package-agreements

# Otherwise download the vendor's signed installer from the advisory URL above,
# verify its Authenticode signature, then install silently.
Get-AuthenticodeSignature "$env:TEMP\kimai-patched.msi" | Format-List
Start-Process -FilePath "$env:TEMP\kimai-patched.msi" -ArgumentList '/qn /norestart' -Wait

# Confirm via Get-Package.
Get-Package | Where-Object { $_.Name -match 'kimai' }


# Fleet check: re-scan with your vulnerability scanner.
# (Nessus, Qualys, Tenable, OpenVAS) - confirm the scanner no longer flags CVE-2026-23626.

Verify the fix landed


# 1. Confirm the running version matches the fixed-in version listed above.
# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.
# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl --since "10 minutes ago" | tail -50
dmesg --since "10 minutes ago" 2>/dev/null | tail -50

If you cannot patch immediately

Block the affected endpoint or input from untrusted users. There is no configuration-only mitigation; patch is required.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in kimai, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-23626 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-23626?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for kimai run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*