# CVE-2026-44903: Prometheus: Stored XSS via crafted histogram bucket label values in the heatmap display of the old Prometheus web UI > Attackers can execute JavaScript in Prometheus users' browsers via crafted histogram labels in the legacy web UI, requiring the old-ui feature flag. - **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 26 May 2026 - **Updated:** 27 May 2026 - **Also known as:** BIT-prometheus-2026-44903, CLEANSTART-2026-CD57328, CLEANSTART-2026-DS50998, CLEANSTART-2026-GK28473, CLEANSTART-2026-KD10786, CLEANSTART-2026-PY51486, CLEANSTART-2026-TZ27062, CLEANSTART-2026-YK40300, DEBIAN-CVE-2026-44903, ECHO-5d42-bdf2-d207, GHSA-fw8g-cg8f-9j28, GO-2026-5381, MINI-25rm-wjp3-qgcq, MINI-2fgp-whxh-wh29, MINI-2p3f-pww9-2c7c, MINI-373w-765w-53w2, MINI-39cj-rmjw-xwhx, MINI-39cp-qx94-6gjw, MINI-3cx3-2w2h-2mx6, MINI-3v37-c4q7-p5xf, MINI-45r6-v9cr-rf3g, MINI-4h2m-3gwg-qq76, MINI-4mr2-4w7j-mq7m, MINI-4mr6-wggq-c6xg, MINI-4ppx-7crr-pqx2, MINI-4vcx-3g9h-qwph, MINI-5338-rqx4-27jf, MINI-5799-gr8j-j894, MINI-5cq5-f8h3-v6q3, MINI-5gvr-w2j8-wmxc, MINI-5pfv-33mq-7vgv, MINI-64f9-2cg6-jcg7, MINI-6693-rpx9-3w8f, MINI-67gm-4frh-gmmv, MINI-67jc-m629-pm44, MINI-6g3h-w359-4379, MINI-6pvw-62j2-4vf2, MINI-6xrm-97xq-f9pm, MINI-7242-9qpp-5cp7, MINI-73fm-9ffx-h28c, MINI-79h2-q3m2-p8px, MINI-7j4x-cm87-qv2g, MINI-7qm9-7v7r-w6g8, MINI-7x4c-p574-5gch, MINI-7xf3-73r4-38r7, MINI-887p-mmgq-qcwr, MINI-89hp-3c7x-24p9, MINI-8mq3-x96h-h8vr, MINI-92v9-3vph-39v8, MINI-94m8-g962-6w64, MINI-94rx-2h2c-qhc8, MINI-953g-2hx7-gcg2, MINI-97cm-3x24-hxj6, MINI-9fwh-5rj7-8564, MINI-9h8p-7qwf-mvpg, MINI-9p2x-9vvr-w5c7, MINI-9xr2-228q-8x67, MINI-c337-p65p-96p3, MINI-c4w9-4952-q8px, MINI-cpwh-6p39-325j, MINI-f329-q9w3-h7px, MINI-f59f-gv83-xh38, MINI-f7p2-4pm8-gqp7, MINI-f8h9-7827-3j9w, MINI-f8p6-48hv-93wh, MINI-f8v2-7wj2-537p, MINI-fqg8-rx7w-24q9, MINI-fr6m-pfm6-jxx7, MINI-fxq7-j92r-rm9x, MINI-g87j-fv42-888r, MINI-g9qm-vchh-pm28, MINI-ggh3-cxx7-mpf2, MINI-gjmm-3hfj-h4jj, MINI-gqfq-vjvg-7rcp, MINI-grxf-2r65-xcp2, MINI-gw3r-v73v-c6f8, MINI-h544-m2j5-5363, MINI-hg6x-j2p3-7288, MINI-hhp2-rvgr-88cx, MINI-hhvf-fwpq-9r9g, MINI-hm4v-6c35-vrhh, MINI-hpc7-f9fr-jj7x, MINI-hx45-7824-q7cc, MINI-j47v-gh73-764j, MINI-j7gw-2hmh-qwr4, MINI-jhrr-5935-rvfg, MINI-jr6c-272f-gc7q, MINI-m874-g8h8-p6g8, MINI-m8mh-c79j-376v, MINI-mpc2-6fq2-gwgc, MINI-mpj3-v4c6-qr4v, MINI-mq3x-w2g4-76xr, MINI-mq7r-vm4x-9f55, MINI-mwmm-r7r3-5g23, MINI-p2r4-m42q-9938, MINI-p459-42r5-px62, MINI-p4hw-h8hp-cg7g, MINI-p68j-xgfx-92rw, MINI-p8p4-499v-hx85, MINI-pjwm-434m-wfhg, MINI-pmxq-c4mw-884c, MINI-pv5x-f5mc-4hwc, MINI-q49m-h826-3fhx, MINI-q4r3-cjfr-wgp7, MINI-q582-crrc-fxc9, MINI-q6wm-2crv-v5fj, MINI-q84c-vw8r-2fxh, MINI-qch2-6v23-q4h9, MINI-qf9j-chxm-6297, MINI-qrqh-8fh4-hh6q, MINI-qv35-98wj-6r4g, MINI-r6vj-vmqv-82r8, MINI-r9pw-87xp-6hc7, MINI-r9x2-f872-x527, MINI-rf4v-cjcc-pr9r, MINI-rg7j-xggw-82vq, MINI-rm4c-5hcm-vg5p, MINI-v2xc-c356-wpm4, MINI-vf3j-q8wp-j58g, MINI-vh46-mqww-88jf, MINI-vm2j-cvvq-667c, MINI-vp76-gcr9-hmf9, MINI-vpc7-xpgq-3g9h, MINI-vw5x-cmj2-3c4g, MINI-vxp6-4hxh-32x8, MINI-w245-f5qp-j5ww, MINI-w285-r286-9rxf, MINI-w5jr-mvv2-q57w, MINI-w9q3-q8qp-f7fm, MINI-wqw4-j54j-fxp6, MINI-wvwx-8cgq-q4cp, MINI-x463-jg7c-h9ch, MINI-x5r9-mjx6-gwcm, MINI-x5vm-2crw-m5g6, MINI-x98h-8fx7-r8jv, MINI-xmxw-g37c-6rmc, MINI-xwx3-38jr-5fq9, MINI-xxgv-p846-fp6g, ROOT-APP-GOBINARY-CVE-2026-44903, ROOT-APP-GOBINARY-GHSA-fw8g-cg8f-9j28, UBUNTU-CVE-2026-44903 ## What is CVE-2026-44903? CVE-2026-44903 is a medium-severity cross-site scripting vulnerability in prometheus, published on 26 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link. ### Official description 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. Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation) ## Which versions are affected by CVE-2026-44903? 4 open source packages ship an affected version, including github.com/prometheus/prometheus and prometheus. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/prometheus/prometheus` | Go | All versions | 0.311.3 | | `github.com/prometheus/prometheus` | Go | All versions | 0.311.3 | | `github.com/prometheus/prometheus` | Go | All versions | 0.311.3 | | `prometheus` | Bitnami | All versions | 0.305.3, 0.311.3, 3.5.3, 3.11.3 | Products: Prometheus Prometheus. ## How do I fix CVE-2026-44903? Upgrade github.com/prometheus/prometheus to 0.311.3 or later. ## Is CVE-2026-44903 being exploited? There is no known exploitation of CVE-2026-44903 in the wild and no public exploit code. ## Other vulnerabilities in prometheus - [CVE-2026-42151](https://insights.sbomify.com/CVE-2026-42151/): Prometheus Azure AD remote write OAuth client secret exposed via config API (high 7.5) - [CVE-2026-42154](https://insights.sbomify.com/CVE-2026-42154/): Prometheus: remote read endpoint allows denial of service via crafted snappy payload (high 7.5) - [CVE-2021-29622](https://insights.sbomify.com/CVE-2021-29622/): Arbitrary redirects under /new endpoint (medium 6.5) - [CVE-2019-3826](https://insights.sbomify.com/CVE-2019-3826/): Cross-site scripting in prometheus (medium 6.1) - [CVE-2026-40179](https://insights.sbomify.com/CVE-2026-40179/): Prometheus: Stored XSS via metric names and label values in web UI tooltips and metrics explorer (medium 5.3) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-44903 and fix it if it is affected. What it is: CVE-2026-44903 is a medium-severity cross-site scripting vulnerability in prometheus, published on 26 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2026-44903 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/prometheus/prometheus (Go): affected all versions; fixed in 0.311.3 - github.com/prometheus/prometheus (Go): affected all versions; fixed in 0.311.3 - github.com/prometheus/prometheus (Go): affected all versions; fixed in 0.311.3 - prometheus (Bitnami): affected all versions; fixed in 0.305.3, 0.311.3, 3.5.3, 3.11.3 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-44903/ (Markdown: https://insights.sbomify.com/CVE-2026-44903/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44903 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44903 - OSV: https://osv.dev/vulnerability/CVE-2026-44903 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-44903/ Summaries are generated and may contain mistakes; the official description above is the record.