Threats / Veritas / CVE-2021-27877
CVE-2021-27877
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Veritas Backup Exec Agent vulnerability
Veritas Backup Exec Agent contains an improper authentication vulnerability in its SHA authentication scheme, allowing unauthorized access to the agent.
Verdict
Today item, not a backlog item.
An attacker can bypass authentication controls in Backup Exec Agent to gain unauthorized access. This vulnerability has been exploited in ransomware campaigns and is actively weaponized in the wild.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
9 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 0.6491 — 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 authentication requests that exploit the weak SHA scheme to bypass agent verification.
Business
Attacker gains unauthenticated access to backup infrastructure without valid credentials.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I establish a foothold within the Backup Exec Agent to enumerate backup repositories and data stores.
Business
Backup systems become a pivot point for lateral movement and reconnaissance across the enterprise.
3
Lateral reach — past segmentation narrative 3
Attacker
I access and exfiltrate backup data or encrypt it for ransom operations.
Business
Critical backup data is compromised, encrypted, or stolen, eliminating recovery options and enabling extortion.
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