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ExpresswayApplication · Cisco

CVE-2021-34715

HIGH · 7.2 CVSS v3.1 Published 2021-08-18
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
78/100
Remediation priority · High
Remotely reachable Zero-click Patch available

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 · unedited
A vulnerability in the image verification function of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow an authenticated, remote attacker to execute code with internal user privileges on the underlying operating system. The vulnerability is due to insufficient validation of the content of upgrade packages. An attacker could exploit this vulnerability by uploading a malicious archive to the Upgrade page of the administrative web interface. A successful exploit could allow the attacker to execute code with user-level privileges (the _nobody account) on the underlying operating system.

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
How this class of weakness works · CWE-347

The application accepts signed data without properly verifying the signature, so an attacker can forge or tamper with content that the system is meant to trust — tokens, updates, licences. Everything built on that trust then becomes unreliable. Remediation is verifying every signature against the correct key and rejecting anything that does not validate.

General guidance for the improper signature verification class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
ExpresswayApplication
Affected:<= x8.8.0
Telepresence Video Communication ServerApplication
Affected:<= x8.8

CVSS 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
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

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 · scoped
Patch available Apply the vendor patch
Vendor patch tools.cisco.com →
Recommended fix Moderate confidence

Expressway: x8.9 or later | Telepresence VCS: x8.9 or later

  1. 1. Back up the current configuration of the Cisco Expressway Series or Telepresence VCS device.
  2. 2. Log in to the administrative web interface of the affected device.
  3. 3. Navigate to the Upgrade page within the maintenance or administration section.
  4. 4. Download the upgrade package from the official Cisco software download center (software.cisco.com) ensuring it is version x8.9 or later for Expressway (or x8.9 for VCS).
  5. 5. Upload the genuine Cisco upgrade package to the Upgrade page.
  6. 6. Follow the on-screen prompts to complete the upgrade process.
  7. 7. After upgrade, verify the system is functioning normally and the version has been updated.
  8. 8. Confirm that the administrative access requires proper authentication to prevent unauthorized uploads.
Caveat Review Cisco release notes for x8.9 for any changes to features, behavior, or configuration that may require adjustment.

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-34715 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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