CVE-2021-27877: Veritas Backup Exec Agent Improper Authentication Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 767 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 64.9%
EPSS score, percentile 99.2 of all scored records
- How severe?
- 8.2 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline . Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://www.veritas.com/support/en_US/security/VTS21-001
- https://nvd.nist.gov/vuln/detail/CVE-2021-27877
Affected products and versions
The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2021-27877 to its Known Exploited Vulnerabilities (KEV) catalog on 7 Apr 2023.
- CISA marks it as known to be used in ransomware campaigns.
- The due date CISA sets for the required action is 28 Apr 2023.
- The CVE record was published on 1 Mar 2021, 767 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 8.2 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 64.9% (percentile 99.2), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
References
More exploited Veritas vulnerabilities
- CVE-2021-27876: Veritas Backup Exec Agent File Access Vulnerability
- CVE-2021-27878: Veritas Backup Exec Agent Command Execution Vulnerability