AlertmanagerApplication · Prometheus
CVE-2023-40577
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAlertmanager handles alerts sent by client applications such as the Prometheus server. An attacker with the permission to perform POST requests on the /api/v1/alerts endpoint could be able to execute arbitrary JavaScript code on the users of Prometheus Alertmanager. This issue has been fixed in Alertmanager version 0.2.51.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a stored Cross-Site Scripting (XSS) vulnerability in Alertmanager where an authenticated attacker with POST permissions on the /api/v1/alerts endpoint can inject arbitrary JavaScript code into alerts. When users view these malicious alerts in the Alertmanager UI, the injected script executes in their browsers, potentially enabling session hijacking or other client-side attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
AlertmanagerApplication
= 0.25.0
Debian LinuxOperating system
= 10.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify Alertmanager versionRun `alertmanager --version` or check the binary metadata to determine the installed version numberAffected if The installed version is 0.25.0 (the affected version)
-
Verify POST access to /api/v1/alertsReview the Alertmanager configuration file (typically alertmanager.yml) for routing rules and access controls that grant POST permissions to the /api/v1/alerts endpointAffected if Unauthenticated or low-privilege users are permitted to POST alerts to the /api/v1/alerts endpoint
-
Inspect stored alerts for malicious contentQuery the Alertmanager API via `curl http://localhost:9093/api/v1/alerts` and examine the labels and annotations of each alert for suspicious script tags, event handlers, or encoded payloadsAffected if Any alert contains JavaScript code, HTML tags, or encoded payloads in alert labels or annotations that were not intentionally configured
-
Review alert ingestion logsExamine Alertmanager logs and any upstream Prometheus logs for incoming POST requests to /api/v1/alerts that contain unusual payload patternsAffected if Recent POST requests to /api/v1/alerts contain XSS payloads in alert fields
You are affected if Alertmanager version 0.25.0 is running AND the /api/v1/alerts endpoint accepts POST requests from users who can inject arbitrary content into alerts.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Alertmanager to version 0.2.51 or later to receive the fix. Additionally, apply the principle of least privilege to restrict who can POST to the /api/v1/alerts endpoint.
Alertmanager 0.2.51
- 1. Back up your current Alertmanager configuration and data directory
- 2. Stop the Alertmanager service
- 3. Download Alertmanager version 0.2.51 from the official GitHub releases
- 4. Replace the existing Alertmanager binary with the version 0.2.51 binary
- 5. Restore your configuration files to the data directory
- 6. Start the Alertmanager service
- 7. Verify the service is running correctly and test the /api/v1/alerts endpoint
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Alertmanager
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-40577 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-40577 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data