CVE-2023-40577Network attack vector

Browser script execution via unchecked generator URL

Published Aug 25, 2023 · Updated Feb 13, 2025

Stored cross-site scripting in Prometheus Alertmanager 0.25.0 allows remote attackers to execute JavaScript through crafted alerts. The Alert view placed an alert's unvalidated generatorURL into the Source link href, permitting non-HTTP schemes such as javascript. The attacker must be able to POST an alert to /api/v1/alerts, and execution occurs in a user's browser when the malicious Source link is activated.

CVSS severity7.5
High
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored cross-site scripting in Prometheus Alertmanager 0.25.0 allows remote attackers to execute JavaScript through crafted alerts. The Alert view placed an alert's unvalidated generatorURL into the Source link href, permitting non-HTTP schemes such as javascript. The attacker must be able to POST an alert to /api/v1/alerts, and execution occurs in a user's browser when the malicious Source link is activated.

The record

CVE
CVE-2023-40577
Published
Aug 25, 2023
Updated
Feb 13, 2025
Vendor
Prometheus
Product
Alertmanager
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 0.25.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Prometheus · Alertmanagerversion=<= 0.25.0

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001User Execution: Malicious Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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