---
id: "CVE-2021-27878"
kind: "vulnerability"
aliases: ["CVE-2021-27878"]
title: "An issue was discovered in Veritas Backup Exec before 21.2"
severity: "critical"
cvss: 9.0
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Veritas Backup Exec Agent", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "veritas backup exec", "fixed": ["21.2"], "affected": "< 21.2", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["backup-exec", "exploited", "infrastructure", "ransomware", "veritas", "windows"]
not_affected_if: ["no-backup-exec-agent-installed"]
published_at: "2021-03-01T22:15:14+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T22:29:04+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-27878", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-27878", "first_seen_at": "2026-10-23T22:29:04+00:00"}]
---

# An issue was discovered in Veritas Backup Exec before 21.2

Veritas Backup Exec Agent contains a command execution flaw in its data management protocol handling. An attacker can send a crafted protocol command to run arbitrary commands on the machine running the agent.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Veritas Backup Exec Agent affected ? fixed ?
- vendor:veritas backup exec affected < 21.2 fixed 21.2

## Fix

Apply the updates per the vendor instructions (Veritas advisory not fetched; unknown which version is fixed).

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-27878
- 2026-10-23T22:29:04+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-27878

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_