CVE-2026-42267

Any ROLE_USER 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 <f>SUM(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.

// src/Export/Package/CellFormatter/ArrayFormatter.php:24
return implode(', ', $value);  // no sanitizeDDE() call

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.
2. Admin has to export timesheets to Excel version via /en/export/ endpoint.

Fixes

1. Prevent = being part of the tag name (and other fields as well)
2. Use OpenSpout TextCell for everything that is a string

• Any ROLE_USER can plant a formula that executes on the workstation of any user who exports and opens timesheet data
• A single malicious tag poisons all future exports across all users and date ranges until the tag is deleted

CVE-2026-42267 has a CVSS score of 5.7 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.54.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-42267? CVE-2026-42267 is a medium-severity security vulnerability in kimai/kimai (composer), affecting versions >= 2.27.0, <= 2.53.0. It is fixed in 2.54.0.
2. How severe is CVE-2026-42267? CVE-2026-42267 has a CVSS score of 5.7 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of kimai/kimai are affected by CVE-2026-42267? kimai/kimai (composer) versions >= 2.27.0, <= 2.53.0 is affected.
4. Is there a fix for CVE-2026-42267? Yes. CVE-2026-42267 is fixed in 2.54.0. Upgrade to this version or later.
5. Is CVE-2026-42267 exploitable, and should I be worried? Whether CVE-2026-42267 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42267 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42267? Upgrade kimai/kimai to 2.54.0 or later.