CVEs / CVE-2021-27877

CVE-2021-27877: Veritas Backup Exec Agent Improper Authentication Vulnerability

Known exploited in the CISA KEV catalog since 7 Apr 2023
critical 9.8 CVSS 3.1 (NVD)
EPSS 64.9% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
Last changed at its sources 17 Jun 2026

Are you affected? Check your servers with Stackurity: it lists the software on each server and the vulnerabilities to fix first.

Check your servers with Stackurity Already using Stackurity? Search for CVE-2021-27877

Summary

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.
CISA, Known Exploited Vulnerabilities catalog

Description

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.
The CVE record, via NVD · published 1 Mar 2021 · NVD status: Analyzed

Affected and fixed versions

As stated by the CVE record (from the CNA)
Product	Affected	Fixed in
n/a n/a	n/a	—

Exploitation

In CISA KEV since	7 Apr 2023
Due date for US federal agencies	28 Apr 2023
Used in ransomware campaigns	Known
Required action	Apply updates per vendor instructions.

Severity

CVSS 3.1	9.8 critical `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` Scored by NVD

References

CVE-2021-27877 on NVD
CVE-2021-27877 in the CISA KEV catalog
https://www.veritas.com/support/en_US/security/VTS21-001 (cited by CISA)
http://packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
https://www.veritas.com/content/support/en_US/security/VTS21-001#issue1 Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27877 US Government Resource

Sources

Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.

This product uses data from the NVD API but is not endorsed or certified by the NVD.