Cloudanix VulnDB

GHSA-fw8g-cg8f-9j28

None

Prometheus vulnerable to stored XSS via crafted histogram bucket label values in the old web UI heatmap display

CVSS

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EPSS

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Published

May 5, 2026

CISA due date

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The record

In the Prometheus server's legacy web UI (enabled via the command-line flag `--enable-feature=old-ui`), the histogram heatmap chart view does not escape `le` label values when inserting them into the HTML for use as axis tick mark labels. An attacker who can inject crafted metrics (e.g. via a compromised scrape target, remote write, or OTLP receiver endpoint) can execute JavaScript in the browser of any Prometheus user who views the metric in the heatmap chart UI. From the XSS context, an attacker could for example: - Read `/api/v1/status/config` to extract sensitive configuration (although credentials / secrets are redacted by the server) - Call `/-/quit` to shut down Prometheus (only if `--web.enable-lifecycle` is set) - Call `/api/v1/admin/tsdb/delete_series` to delete data (only if `--web.enable-admin-api` is set) - Exfiltrate metric data to an external server Note that this only affects users who have explicitly enabled the legacy Prometheus web UI using the `--enable-feature=old-ui` command-line flag.

Affected packages

Ecosystem Package Introduced Fixed

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