Threats / Veritas / CVE-2021-27876
CVE-2021-27876
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Veritas Backup Exec Agent vulnerability
Veritas Backup Exec Agent contains an authentication bypass vulnerability allowing attackers to access files through specially crafted data management protocol commands.
Verdict
Today item, not a backlog item.
CVE-2021-27876 is an authentication weakness in Backup Exec Agent that permits unauthorized file access. The vulnerability has been exploited in active ransomware campaigns, making it a critical risk for organizations relying on this backup infrastructure.
CISA KEV Yes · 2023-04-073Ransomware use Flagged3EPSS 0.13173 (verify live)4Exploit Weaponized · public PoC5
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
10 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-04-07), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.13173 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Veritas, Backup Exec Agent. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-287 Improper Authentication — weakness family: Authentication.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft malicious data management protocol commands to bypass authentication controls on the Backup Exec Agent.
Business
Attackers gain unauthorized access to backup infrastructure, a primary target for ransomware deployment and data exfiltration.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I read sensitive files stored on or accessible through the compromised Backup Exec Agent machine.
Business
Confidential data including backup metadata, credentials, and business-critical information is exposed to threat actors.
3
Lateral reach — past segmentation narrative 3
Attacker
I use file access to identify backup locations and encryption keys, then deploy ransomware across the environment.
Business
Ransomware campaigns succeed by neutralizing backup defenses, forcing costly recovery operations or ransom payments.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05