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CVE-2021-27877

96
FAUCET Score

CVE-2021-27877 is a critical vulnerability affecting Veritas Backup Exec versions prior to 21.2, stemming from an unpatched, legacy SHA authentication scheme that allows remote attackers to gain unauthorized access and execute privileged commands on an Agent. With a CVSS score of 9.8 (CRITICAL), this vulnerability is easily exploitable over the network without authentication or user interaction, leading to complete compromise of confidentiality, integrity, and availability. It is actively exploited in the wild, notably by the ALPHV (BlackCat) ransomware group, with public exploit modules available in Metasploit and Nuclei, and has garnered significant community and media attention.

Impacted Technologies

VendorProductVersion(s)CPE
< 21.2CPE matchmatch criteria
cpe:2.3:a:veritas:backup_exec:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.2HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
4.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
64.91%
Probability of exploitation in next 30 days
EPSS Percentile
99.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
Added to KEV · Apr 7, 2023
Metasploit: Veritas Backup Exec Agent Remote Code Execution · Mar 1, 2021
Nuclei: CVE-2021-27877 · Oct 22, 2025
This CVE's current EPSS score of 0.6491 is in the 97th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
packetstormsecurity.com / files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html
ExploitThird Party AdvisoryVDB Entry
veritas.com / content/support/en_US/security/VTS21-001
Vendor Advisory