CVE-2021-27877
CVE-2021-27877 is a security flaw in Veritas Backup Exec Agent, backup software companies use. Attackers can get into Veritas Backup Exec Agent without a valid password. 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 an improper authentication in Veritas Backup Exec Agent. In its words: “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.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is improper authentication (CWE-287), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, 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 65%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
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 9.8.[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 65%.[4] |
See also
Other Veritas Backup Exec Agent flaws
- CVE-2021-27878: command execution ·
- 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-2021-27878, Veritas Backup Exec Agent: command execution ·
- 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 Improper Authentication Vulnerability”. Known Exploited Vulnerabilities Catalog, added 7 Apr 2023.
- ^ National Institute of Standards and Technology. “CVE-2021-27877 Detail”. National Vulnerability Database, published 1 Mar 2021.
- ^ Veritas. Advisories and fixes: veritas.com, veritas.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.649, percentile 99.2, 31 Oct 2026.
- CVE Program. “CVE-2021-27877”. 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.