CVE-2026-77900: Microsoft Azure App Service for Linux

Azure App Service Remote Code Execution Vulnerability

CVSS 9.8 CriticalCriticalEPSS 0.0072 · 54th percentile

Critical, because:

CVSS score 9.8: 9.0 or more.

Published by the CVE Program (CNA: microsoft) at 8 Oct 2026, 22:15 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Microsoft	Azure App Service for Linux	affected -

Identifiers

CVE-2026-77900

CNA

microsoft

Weakness (CWE)

CWE-306

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Microsoft Azure App Service for Linux is affected by a missing authentication flaw in a critical function, and the source does not list affected versions. An unauthenticated attacker with network access can execute code on the service. The source lists no fix or workaround.

Written 11 Nov 2026.

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
9.8	Critical	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C	CNA (microsoft)

CISA KEV Not listed.
EPSS 0.0072, the 54th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

8 Oct 2026, 22:15 UTC Confirmed by the CVE List
31 Oct 2026, 16:31 UTC First seen by agentprime

Sources

References from the CNA

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77900 vendor-advisorypatch

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.