CVE-2021-27876: Veritas Backup Exec Agent File Access Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 7 Apr 2023, 767 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 13.5%
EPSS score, percentile 96.4 of all scored records
- How severe?
- 8.1 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline 28 Apr 2023. 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 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 28 April 2023.
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-2021-27876
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 28 Oct 2026. About the data.
About this vulnerability
Veritas Backup Exec (BE) Agent contains a file access vulnerability that could allow an attacker to specially craft input parameters on a data management protocol command to access files on the BE Agent machine.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2021-27876 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 8.1 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 13.5% (percentile 96.4), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
An issue was discovered in Veritas Backup Exec before 21.2. The communication between a client and an Agent requires successful authentication, which is typically completed over a secure TLS communication. However, due to a vulnerability in the SHA Authentication scheme, an attacker is able to gain unauthorized access and complete the authentication process. Subsequently, the client can execute data management protocol commands on the authenticated connection. By using crafted input parameters in one of these commands, an attacker can access an arbitrary file on the system using System privileges.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. 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 |
|---|---|
| 1 Mar 2021 | CVE record published |
| 7 Apr 2023 | Added to CISA KEV |
| 28 Apr 2023 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited Veritas vulnerabilities
- CVE-2021-27877: Veritas Backup Exec Agent Improper Authentication Vulnerability
- CVE-2021-27878: Veritas Backup Exec Agent Command Execution Vulnerability