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CriticalVulnerabilityCVE-2026-76466updated 25 Oct 2026, 19:06 UTC

Cisco Expressway: remote attackers can run commands as root

Attackers on the network who obtain certain login cookies can take full control of the device. Some certificate checks in clustering are also skipped, making this easier.

Official, 2 sources
SeverityCriticalCVSS 9.8 of 10
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker on networkNeeds network access to the device
  2. 2Steals persistent cookiesCookies are reusable, persistent credentials
  3. 3Calls database service RPCUnauthenticated remote procedure calls
  4. 4Runs commands as rootClient certificates are not validated
  5. ResultAttacker controls the appliance as root

What happened

A flaw in the database service of Cisco Expressway Series (Expressway-C and Expressway-E) combines persistent cookies with insufficient client certificate validation when TLS Verify Mode is enabled for clustering. An attacker with the cookies can invoke specific RPC commands on the database service to run arbitrary OS commands as root.

Why it is dangerous: Successful exploitation gives the attacker root on the underlying operating system of the appliance, which handles video and voice call traffic. Any organization running affected Expressway devices is at risk.

Are you affected?

You are affected if you run Cisco Expressway Core (Expressway-C) or Expressway Edge (Expressway-E) devices with the database service and TLS Verify Mode enabled for clustering.

Cisco Expressway Series: Expressway-C and Expressway-E devices (affected versions not specified in the provided material).

What to do

  1. Check whether your Cisco Expressway-C or Expressway-E devices have TLS Verify Mode enabled for clustering.
  2. Check the official Cisco security advisory for a fixed software version and update your devices to it.
  3. Restrict network access to Expressway devices to trusted hosts until patched.

Timeline

  1. 21 Oct 2026, 17:19 UTC
    Publicly disclosed
  2. 21 Oct 2026, 17:19 UTC
    Reported by NVD · NVD
  3. 25 Oct 2026, 19:06 UTC
    GitHub Advisory reported on it · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-76466 · GHSA-p2jr-qv63-hjch
CVSS
9.8 / 10
EPSS
0.4% chance of exploitation within 30 days
Disclosed
21 Oct 2026, 17:19 UTC
On Zero Radar
before the radar started
Last change
25 Oct 2026, 19:06 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Cisco Expressway: remote attackers can run commands as root · Zero Radar