vulnerability / NVI-00004891 / Revision 3
Kimai vulnerable to formula Injection via tag names in XLSX export
GitHub lists this reviewed advisory for kimai/kimai. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.7 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
5.7 MEDIUM (3.1)
nvd@nist.gov severity; no combined Null risk score.
5.4 MEDIUM (4.0)
security-advisories@github.com severity; no combined Null risk score.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
kimai/kimai
source listed>= 2.27.0, <= 2.53.0
## 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 `SUM(54+51)` 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. ```php // 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
kimai/kimai
source listedECOSYSTEM: introduced 2.27.0; fixed 2.54.0
## 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 `SUM(54+51)` 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. ```php // 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
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. NIST National Vulnerability Database
- vendor patch
The original advisory lists fixed boundaries 2.54.0 for kimai/kimai. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-3xc2-h5r3-wv3r ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- GHSA-3xc2-h5r3-wv3r ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-42267 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.