CVE-2021-27878
Veritas Backup Exec Agent Command Execution Vulnerability
Veritas Backup Exec Agent
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. The attacker could use one of these commands to execute an arbitrary command on the system using system privileges.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 7 April 2023. US federal agencies were required to remediate it by 28 April 2023. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 24%, which is higher than 97.8% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2021-27878 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2021-27878.
What does CVE-2021-27878 affect?
CVE-2021-27878 affects Veritas Backup Exec Agent. 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. The attacker could use one of these commands to execute an arbitrary command on the system using system privileges.
How severe is CVE-2021-27878?
CVE-2021-27878 is rated HIGH with a CVSS base score of 8.8. EPSS puts the probability of exploitation in the next 30 days at 24%, higher than 97.8% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 28 April 2023.
How should organisations respond to CVE-2021-27878?
Apply the vendor patch for Veritas Backup Exec Agent as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.