What is CVE-2025-55321?

CVE-2025-55321 is a critical-severity vulnerability in Microsoft Azure Monitor, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2025-10-09.

How severe is CVE-2025-55321?

Critical severity. CVSS v3 base score is 9.3 out of 10.

Is CVE-2025-55321 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XSS in Microsoft Azure Monitor

CVE-2025-55321

Improper neutralization of input during web page generation ('cross-site scripting') in Azure Monitor allows an unauthorized attacker to perform spoofing over a network.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2025-10-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (36.0th percentile), scored 2026-09-27.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000

Affected products

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

fkie-cad/nvd-json-data-feeds

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55321 (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2025-55321?: CVE-2025-55321 is a critical-severity vulnerability in Microsoft Azure Monitor, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2025-10-09.
How severe is CVE-2025-55321?: Critical severity. CVSS v3 base score is 9.3 out of 10.
Is CVE-2025-55321 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.