Prometheus is an open-source monitoring system and time series database. From 2.49.0 to before 3.5.3 and 3.11.3, 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 can execute JavaScript in the browser of any Prometheus user who views the metric in the heatmap chart UI. This vulnerability is fixed in 3.5.3 and 3.11.3.
Prometheus is an open-source monitoring system and time series database. From 2.49.0 to before 3.5.3 and 3.11.3, 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 can execute JavaScript in the browser of any Prometheus user who views the metric in the heatmap chart UI. This vulnerability is fixed in 3.5.3 and 3.11.3.
Prometheus is an open-source monitoring system and time series database. From 2.49.0 to before 3.5.3 and 3.11.3, 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 can execute JavaScript in the browser of any Prometheus user who views the metric in the heatmap chart UI. This vulnerability is fixed in 3.5.3 and 3.11.3.
### Impact
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.
### Patches
https://github.com/prometheus/prometheus/commit/38f23b9075ced1de2b82d2dad8b2bebb1ecd5b7d
### Workarounds
If at all possible, disable the legacy web UI by removing the `--enable-feature=old-ui` command-line flag).
If this is not an option, take the following precautions:
- If using the remote write receiver (`--web.enable-remote-write-receiver`), ensure it is not exposed to untrusted sources.
- If using the OTLP receiver (`--web.enable-otlp-receiver`), ensure it is not exposed to untrusted sources.
- Ensure scrape targets are trusted and not under attacker control.
- Do not enable admin / mutating API endpoints (e.g. `--web.enable-admin-api` or `web.enable-lifecycle`) in cases where you cannot prevent untrusted data from being ingested.
- Users should avoid clicking untrusted links, especially those containing functions such as `label_replace`, as they may generate poisoned label names and values.
### References
- CVE-2019-10215 — prior stored DOM XSS vulnerability in Prometheus query history, fixed in v2.7.2
- CVE-2026-40179 — prior stored DOM XSS vulnerability in Prometheus web UI (hover tooltips and metrics explorer), fixed in v3.11.2
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: May 26, 2026, 9:27:18 PM
dateUpdated: May 27, 2026, 2:20:35 PM
1 related source bulletins · separate from aliases
WID-SEC-W-2026-1292: Prometheus: Mehrere Schwachstellen
CVE-2026-42151 · CVE-2026-42154 · CVE-2026-44903
No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Analyzed
Weakness classifications: CWE-79
Original publisher date fields
published: 2026-05-26T22:16:43.010
lastModified: 2026-07-24T12:10:00.210
1 source CPE criteria · context only
cpe:2.3:a:prometheus:prometheus:*:*:*:*:*:*:*:*
The original JSON retains the logical configuration operators, exclusions and version bounds.
No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.