Kimai vulnerable to formula Injection via tag names in XLSX export

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-42267: 0.22% estimated exploitation activity in the next 30 days; percentile 12.64 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Any ROLEUSER can create a tag with a formula string as its name (e.g. =SUM(54+51)) via POST /api/tags and assign it to a timesheet. When an admin exports timesheets to XLSX, ArrayFormatter.formatValue() joins tag names with implode() and returns the result unchanged. OpenSpout promotes any =-prefixed string to a FormulaCell, writing <fSUM(54+51)</f into the XLSX archive. Excel evaluates the formula when the file is opened. Details 1. ArrayFormatter does not sanitize before returning sanitizeDDE() exists on StringHelper and is called by TextFormatter, but ArrayFormatter never calls it. 2. Tag name validation does not block formula trigger characters The API blocks commas in tag names but permits =, +, -, and @ - all valid formula prefixes in Excel and LibreOffice Calc. 3. OpenSpout silently promotes strings to formula cells Cell::fromValue("=SUM(54+51)") returns a FormulaCell with no warning. PoC 1. It logs in as normal user, creates tag =SUM(54+51), assigns it to a timesheet.…

Published by the source

5 May 2026, 20:53 UTC

Last modified by the source

14 May 2026, 20:31 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3xc2-h5r3-wv3r

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# Patch Next advisory brief: CVE-2026-42267

Advisory: Kimai vulnerable to formula Injection via tag names in XLSX export
IDs: CVE-2026-42267, GHSA-3xc2-h5r3-wv3r
Record: https://patchnext.com/advisories/cve-2026-42267 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: kimai/kimai 2.54.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist kimai/kimai: affected >= 2.27.0, <= 2.53.0; fixed in 2.54.0

## Suggested inspection (read-only)
- Packagist kimai/kimai: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on kimai/kimai.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3xc2-h5r3-wv3r (GitHub-reviewed advisory GHSA-3xc2-h5r3-wv3r lists affected ranges: Packagist kimai/kimai >=2.27.0 <=2.53.0)

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