Threats / Veritas / CVE-2021-27877
CVE-2021-27877
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
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.
CISA KEV Yes · 2023-04-075Ransomware use Flagged5EPSS 0.6491 (verify live)6Exploit Weaponized · public PoC7CVSS 8.23CISA SSVC Exploitation: active · Automatable: yes · Impact: partial4
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
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
CVSS 8.2 (CVSS:3.1/AC:L/AV:N/A:N/C:H/I:L/PR:N/S:U/UI:N) · Affected: Veritas, Backup Exec Agent. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-287 Improper Authentication — weakness family: Authentication.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 767 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a functional/weaponized public exploit). Catalog entries: Metasploit module, nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
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