CVE-2021-27876
HighExploitedPublic exploitThe communication between a client and an Agent requires successful authentication, which is typically completed over a secure TLS communication.
Published Mar 1, 2021 · Updated Nov 3, 2025
Key Facts
Patch immediately- CVE-2021-27876 is a high-severity vulnerability (CVSS 8.1 v3.1) affecting Backup Exec (Veritas).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Apr 3, 2023 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 14% probability of exploitation in the next 30 days.
- Fixed versions are available, including Backup Exec 21.2.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
8.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
EPSS (30-day exploit likelihood)
14%
Higher than 96.4% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-27876 brief as a PDF
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Apr 7, 2023 | Apr 28, 2023 | Known |
| Industry KEV feed | Apr 3, 2023 | Apr 28, 2023 | Known |
| CIRCL KEV | Apr 7, 2023 | Apr 28, 2023 | Known |
| ENISA EUVD | Apr 7, 2023 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
1 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Backup ExecVeritas | See advisory | 21.2 |
Patched Releases
Backup Exec
21.2
Timeline
Publicly disclosed
Mar 1, 2021
Added to Industry KEV feed
Apr 3, 2023
Added to CISA KEV
Apr 7, 2023
Added to CIRCL KEV
Apr 7, 2023
Added to ENISA EUVD
Apr 7, 2023
Last updated
Nov 3, 2025
References
- advisoryhttps://www.veritas.com/content/support/en_US/security/VTS21-001#issue2
- exploithttp://packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
An issue was discovered in Veritas Backup Exec before 21.2.
Affected: Backup Exec (Veritas). The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Apr 3, 2023 and is known to be used in ransomware campaigns.
Yes. It was added on Apr 7, 2023 with a federal remediation due date of Apr 28, 2023.
Public exploit code is available.
Fixed versions are available, including Backup Exec 21.2.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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