CVE-2026-44903
Stored XSS in Prometheus Legacy Web UI Heatmap Chart
Publication date: 2026-05-26
Last updated on: 2026-05-26
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| prometheus | prometheus | From 2.49.0 (inc) to 3.5.3 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | 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. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Prometheus monitoring system's legacy web UI, specifically in the histogram heatmap chart view. The issue is that label values are not properly escaped when inserted into the HTML for axis tick mark labels. As a result, an attacker who can inject specially crafted metrics can execute arbitrary JavaScript code in the browser of any user who views the affected heatmap chart UI.
This vulnerability affects Prometheus versions from 2.49.0 up to but not including 3.5.3 and 3.11.3, and it is fixed in versions 3.5.3 and 3.11.3.
How can this vulnerability impact me? :
The vulnerability allows an attacker to execute JavaScript code in the browser of any Prometheus user who views the compromised heatmap chart UI. This can lead to cross-site scripting (XSS) attacks, potentially resulting in unauthorized actions performed on behalf of the user, theft of sensitive information such as session tokens, or other malicious activities within the user's browser context.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, upgrade your Prometheus server to version 3.5.3 or 3.11.3 or later, where the issue is fixed.
Alternatively, disable the legacy web UI by not enabling the --enable-feature=old-ui flag, as the vulnerability exists only in the legacy UI.