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MEDIUM severity

Kimai has Stored XSS via Incomplete HTML Attribute Escaping in Team Member WidgetGHSA-g82g-m9vx-vhjg

MEDIUMFix: kimai/kimai#2959

GHSA-g82g-m9vx-vhjg is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in kimai/kimai. A fix is available for kimai/kimai — see the affected versions and patch details below.

Also known asCVE-2026-40479
Published
Updated
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 GHSA-g82g-m9vx-vhjg.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs11th percentile — riskier than 11% of all scored CVEsHighest risk
0.00%0.25%0.50%0.75%0.0%0.2%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

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

The client-side escapeForHtml() function in KimaiEscape.js, introduced in commit 89bfa82c (#2959) to fix a JavaScript XSS vulnerability, only escapes <, >, and & but does not escape " (double quote) or ' (single quote). When user-controlled data (profile alias) is placed in an HTML attribute context (title="__DISPLAY__") via the team member form prototype and rendered through innerHTML, the missing quote escaping allows HTML attribute injection, resulting in Stored XSS.

Details

Incomplete security patch. The escapeForHtml() function was meant to prevent XSS but missed quote characters, which are critical for HTML attribute context escaping.

Vulnerable code — assets/js/plugins/KimaiEscape.js:29-33:

const tagsToReplace = {
    '&': '&amp;',
    '<': '&lt;',
    '>': '&gt;',
    // MISSING: '"': '&quot;'
    // MISSING: "'": '&#039;'
};

Affected code files:

  • assets/js/plugins/KimaiEscape.js:24-38 — incomplete escape function
  • assets/js/forms/KimaiTeamForm.js:77,86 — replacement + innerHTML
  • templates/macros/widgets.html.twig:126 — title="{{ tooltip }}" in avatar macro
  • templates/form/blocks.html.twig:104 — {{ widgets.avatar('__INITIALS__', '__COLOR__', '__DISPLAY__') }}

PoC

poc.zip

Please extract the uploaded compressed file before proceeding

  1. ./setup.sh
  2. ./poc_xss.sh
<img width="751" height="155" alt="스크린샷 2026-04-07 오후 9 06 27" src="https://github.com/user-attachments/assets/c09a23fb-f60b-49dd-9018-8c723e35b4c4" />

Impact

  • Stored XSS: payload persists in the database (user alias field)
  • Privilege escalation: ROLE_USER injects XSS that executes in ROLE_ADMIN/ROLE_SUPER_ADMIN browser session

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistkimai/kimaiall versions2.53.0composer require kimai/kimai:^2.53.0

Affected Products

1 product · 1 configurations
Application
kimaikimai
< 2.53.0
range

Detection & mitigation playbook

Open-source dependency

  1. 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.

  2. Fix

    Update kimai/kimai to 2.53.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g82g-m9vx-vhjg is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Summary The client-side `escapeForHtml()` function in `KimaiEscape.js`, introduced in commit `89bfa82c` (#2959) to fix a JavaScript XSS vulnerability, only escapes `<`, `>`, and `&` but does not escape `"` (double quote) or `'` (single quote). When user-controlled data (profile alias) is placed in an HTML attribute context (`title="__DISPLAY__"`) via the team member form prototype and rendered through `innerHTML`, the missing quote escaping allows HTML attribute injection, resulting in Stored XSS. ### Details Incomplete security patch. The `escapeForHtml()` function was meant to prevent X
O3 Security · Impact-Aware SCA

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Kimai has Stored XSS via Incomplete HTML Attribute…