How severe is CVE-2026-42267?

No CVSS score has been assigned to CVE-2026-42267 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42267?

CVE-2026-42267 affects the following packages: kimai/kimai (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-42267?

Update kimai/kimai to 2.54.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42267 is resolved across your whole dependency graph.

How do I detect CVE-2026-42267 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kimai/kimai, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42267 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-42267 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42267 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42267?

CVE-2026-42267 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 13th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42267?

CVE-2026-42267 is classified as CWE-1236 (CWE-1236). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42267 published, and has it been updated?

CVE-2026-42267 was published on May 8, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-42267 — kimai

CVE-2026-42267 is a CWE-1236 vulnerability in kimai/kimai. A fix is available for kimai/kimai — see the affected versions and patch details below.

Kimai: Formula Injection via tag names in XLSX export

Also known asGHSA-3xc2-h5r3-wv3r

Published

May 8, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42267.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs13th percentile — riskier than 13% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐘kimai/kimai

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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

It logs in as normal user, creates tag =SUM(54+51), assigns it to a timesheet.
Admin has to export timesheets to Excel version via /en/export/ endpoint.

Impact

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

Fixes

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`kimai/kimai`	≥ 2.27.0&&< 2.54.0	2.54.0`composer require kimai/kimai:^2.54.0`

Affected Products

1 product · 1 configurations

Application

kimaikimai

≥ 2.27.0 && < 2.54.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kimai/kimai, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update kimai/kimai to 2.54.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42267 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

## Summary 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 `TextFormat

O3 Security · Impact-Aware SCA

Is CVE-2026-42267 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works