---
id: "CVE-2021-27877"
kind: "vulnerability"
aliases: ["CVE-2021-27877"]
title: "An issue was discovered in Veritas Backup Exec before 21.2"
severity: "critical"
cvss: 9.8
epss: null
exploited: true
status: "open"
category: "other"
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", "other", "ransomware", "veritas", "windows"]
not_affected_if: ["unknown"]
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-2021-27877", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-27877", "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 has an improper authentication flaw in its SHA authentication scheme. An attacker can gain unauthorized access to the agent on a backup host.

_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 vendor updates per Veritas instructions; CISA lists this as a known exploited vulnerability with required action to apply updates.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-27877
- 2026-10-23T22:29:04+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-27877

## From the sources

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.

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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_