CVE-2021-27877 Veritas Backup Exec Agent Improper Authentication Vulnerability
Veritas Backup Exec (BE) Agent contains an improper authentication vulnerability that could allow an attacker unauthorized access to the BE Agent via SHA authentication scheme.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- 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 8.2, scored by Vendor).
- It has been in the catalogue for 1,309 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
An issue was discovered in Veritas Backup Exec before 21.2. It supports multiple authentication schemes: SHA authentication is one of these. This authentication scheme is no longer used in current versions of the product, but hadn't yet been disabled. An attacker could remotely exploit this scheme to gain unauthorized access to an Agent and execute privileged commands.
What To Do Now
- 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
- 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
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
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