CVE-2021-27878
CVE-2021-27878 is a security flaw in Veritas Backup Exec Agent, backup software companies use. Attackers are using a flaw in Veritas Backup Exec Agent. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 7 Apr 2023, and says ransomware gangs have used it.[1]
Veritas Backup Exec Agent is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Veritas has published a fix or advice.
Description
CISA calls it a command execution in Veritas Backup Exec Agent. In its words: “Veritas Backup Exec (BE) Agent contains a command execution vulnerability that could allow an attacker to use a data management protocol command to execute a command on the BE Agent machine.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is improper authentication (CWE-287), in MITRE’s list of common software weaknesses.
It scores 8.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Veritas’s advisory has them[3]. CISA names the product as Veritas Backup Exec Agent.
Most families won’t have Veritas Backup Exec Agent; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 7 Apr 2023, 767 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 28 Apr 2023 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 24%. That’s in the top 3% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Veritas has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Veritas Backup Exec Agent is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 28 Apr 2023 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 24%.[4] |
See also
Other Veritas Backup Exec Agent flaws
- CVE-2021-27877: improper authentication ·
- CVE-2021-27876: file access ·
Other improper authentication flaws
- CVE-2026-105133, AhsayCBS: improper authentication ·
- CVE-2026-42018, JFrog Artifactory: improper authentication ·
- CVE-2026-82329, JFrog Artifactory: improper authentication ·
- CVE-2026-59822, BerriAI LiteLLM: improper authentication ·
- CVE-2023-49105, ownCloud: improper authentication ·
Added the same day
- CVE-2023-26083, Arm Mali Graphics Processing Unit (GPU): mali GPU kernel driver information disclosure ·
- CVE-2021-27877, Veritas Backup Exec Agent: improper authentication ·
- CVE-2021-27876, Veritas Backup Exec Agent: file access ·
- CVE-2019-1388, Microsoft Windows: certificate dialog privilege escalation ·
Every Veritas flaw on CISA’s list · Everything added in April 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Veritas Backup Exec Agent Command Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 7 Apr 2023.
- ^ National Institute of Standards and Technology. “CVE-2021-27878 Detail”. National Vulnerability Database, published 1 Mar 2021.
- ^ Veritas. Advisories and fixes: veritas.com, veritas.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.240, percentile 97.8, 31 Oct 2026.
- CVE Program. “CVE-2021-27878”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.