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Actively exploitedKnown ransomware use

CVE-2021-27878 Veritas Backup Exec Agent Command Execution Vulnerability

Veritas Backup Exec (BE) Agent contains a command execution vulnerability that could allow an attacker to use a data management protocol command to execute a command on the BE Agent machine.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 7 Apr 2023.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated High severity (CVSS 8.8, scored by Vendor).
  • It has been in the catalogue for 1,309 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

An issue was discovered in Veritas Backup Exec before 21.2. The communication between a client and an Agent requires successful authentication, which is typically completed over a secure TLS communication. However, due to a vulnerability in the SHA Authentication scheme, an attacker is able to gain unauthorized access and complete the authentication process. Subsequently, the client can execute data management protocol commands on the authenticated connection. The attacker could use one of these commands to execute an arbitrary command on the system using system privileges.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Veritas Backup Exec Agent. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 28 Apr 2023 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Veritas Flaws

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CVE-2021-27876 · RansomwareVeritas Backup Exec Agent File Access VulnerabilityAdded 7 Apr 2023CVE-2021-27877 · RansomwareVeritas Backup Exec Agent Improper Authentication VulnerabilityAdded 7 Apr 2023

All 3 exploited Veritas vulnerabilities

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-27878
  3. CVE record: CVE-2021-27878
  4. FIRST EPSS
  5. veritas.com/support/en_US/security/VTS21-001
  6. veritas.com/content/support/en_US/security/VTS21-001#issue3
  7. packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html