CVE-2026-40479: Kimai/kimai Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-g82g-m9vx-vhjg
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2026-40479 is a MODERATE (CVSS 5.4) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Kimai/kimai libraries in the Packagist ecosystem. The issue involves kimai has stored xss via incomplete html attribute escaping in team member widget. Remediation is available by upgrading affected packages to version 2.53.0.

CVE-2026-40479 at a Glance

CVE Identifier CVE-2026-40479
GHSA Identifier GHSA-g82g-m9vx-vhjg
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Kimai/kimai
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 5.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-40479

To remediate this vulnerability, upgrade all affected Kimai/kimai dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

kimai/kimai fixed: 2.53.0 
Upgrade kimai/kimai to 2.53.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for kimai/kimai

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-40479, inspect your project dependencies for Kimai/kimai:

inspect dependencies for kimai/kimai

Analyze the terminal output to locate any version of Kimai/kimai in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.53.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Kimai/kimai, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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`: ```javascript 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](https://github.com/user-attachments/files/26537515/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

CVE-2026-40479 Affected Kimai/kimai Versions

1 component(s)
Fixed Versions:
2.53.0
Product / Package Ecosystem Affected Versions Fixed Version
kimai/kimai
 Packagist
< 2.53.0
2.53.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/kimai/kimai/security/advisories/GHSA-g82g-m9vx-vhjg
NVD — CVE-2026-40479 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40479
Kimai/kimai Source Repository REPOSITORY
https://github.com/kimai/kimai/pull/2959
Kimai/kimai Source Repository REPOSITORY
https://github.com/kimai/kimai
Kimai/kimai Release RELEASE
https://github.com/kimai/kimai/releases/tag/2.53.0

Frequently Asked Questions

What is CVE-2026-40479?
CVE-2026-40479 is a security vulnerability in Kimai/kimai involving Kimai has Stored XSS via Incomplete HTML Attribute Escaping in Team Member Widget under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Kimai/kimai versions are affected?
Affected versions include releases prior to 2.53.0 across affected packages: kimai/kimai.
What version fixes CVE-2026-40479?
Upgrading to 2.53.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is kimai/kimai affected?
Yes, kimai/kimai is affected in releases prior to 2.53.0. Upgrade your dependency to 2.53.0 or later.
What is the CVSS score of CVE-2026-40479?
CVE-2026-40479 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-40479?
CVE-2026-40479 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2026-40479?
Run the dependency tree command: 'inspect dependencies for kimai/kimai'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g82g-m9vx-vhjg",
  "modified" : "2026-04-27T15:20:26Z",
  "published" : "2026-04-15T19:46:35Z",
  "aliases" : [ "CVE-2026-40479" ],
  "summary" : "Kimai has Stored XSS via Incomplete HTML Attribute Escaping in Team Member Widget",
  "details" : "### Summary\nThe 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.\n\n### Details\nIncomplete security patch. The `escapeForHtml()` function was meant to prevent XSS but missed quote characters, which are critical for HTML attribute context escaping.\n\n**Vulnerable code** — `assets/js/plugins/KimaiEscape.js:29-33`:\n```javascript\nconst tagsToReplace = {\n    '&': '&amp;',\n    '<': '&lt;',\n    '>': '&gt;',\n    // MISSING: '\"': '&quot;'\n    // MISSING: \"'\": '&#039;'\n};\n```\n\n**Affected code files**:\n- `assets/js/plugins/KimaiEscape.js:24-38` — incomplete escape function\n- `assets/js/forms/KimaiTeamForm.js:77,86` — replacement + innerHTML\n- `templates/macros/widgets.html.twig:126` — `title=\"{{ tooltip }}\"` in avatar macro\n- `templates/form/blocks.html.twig:104` — `{{ widgets.avatar('__INITIALS__', '__COLOR__', '__DISPLAY__') }}`\n\n### PoC\n[poc.zip](https://github.com/user-attachments/files/26537515/poc.zip)\n\nPlease extract the uploaded compressed file before proceeding\n\n1. ./setup.sh\n2. ./poc_xss.sh\n\n<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\" />\n\n### Impact\n- Stored XSS: payload persists in the database (user alias field)\n- Privilege escalation: ROLE_USER injects XSS that executes in ROLE_ADMIN/ROLE_SUPER_ADMIN browser session",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "kimai/kimai"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.53.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/kimai/kimai/security/advisories/GHSA-g82g-m9vx-vhjg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40479"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kimai/kimai/pull/2959"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/kimai/kimai"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kimai/kimai/releases/tag/2.53.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-15T19:46:35Z",
    "nvd_published_at" : "2026-04-17T23:16:12Z"
  }
}