# CVE-2021-27878: Veritas Backup Exec Agent Command Execution

> An authentication bypass in Veritas Backup Exec allows attackers to execute arbitrary commands with system privileges.

- **Severity:** High 8.8 (`CVSS:3.1/AC:L/AV:N/A:H/C:H/I:H/PR:L/S:U/UI:N`)
- **Exploited in the wild:** Yes, since 7 Apr 2023 (CISA KEV), used in ransomware
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Mar 2021
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-6r93-82vq-9w4w

## What is CVE-2021-27878?

CVE-2021-27878 is a high-severity authentication bypass vulnerability in n/a, published on 1 Mar 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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. The attacker could use one of these commands to execute an arbitrary command on the system using system privileges.

## Which versions are affected by CVE-2021-27878?

It affects 1 product.


Products: Veritas Backup Exec.

## How do I fix CVE-2021-27878?

No fix has been published for CVE-2021-27878 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 28 Apr 2023.

## Is CVE-2021-27878 being exploited?

Yes. Attackers have exploited CVE-2021-27878 in the wild since at least 7 Apr 2023, including in ransomware campaigns.

Public exploit code:

- Veritas Backup Exec Agent Remote Code Execution (metasploit)

## Other vulnerabilities in n/a

- [CVE-2021-27877](https://insights.sbomify.com/CVE-2021-27877/): Veritas Backup Exec Agent Improper Authentication (high 8.2, exploited in the wild)
- [CVE-2021-27876](https://insights.sbomify.com/CVE-2021-27876/): Veritas Backup Exec Agent File Access (high 8.1, exploited in the wild)
- [CVE-2017-8895](https://insights.sbomify.com/CVE-2017-8895/): Use after free in n/a (critical 9.8)
- [CVE-2020-36167](https://insights.sbomify.com/CVE-2020-36167/): Path traversal in n/a (critical 9.3)
- [CVE-2024-33673](https://insights.sbomify.com/CVE-2024-33673/): Privilege escalation in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27878 and fix it if it is affected.

What it is: CVE-2021-27878 is a high-severity authentication bypass vulnerability in n/a, published on 1 Mar 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2021-27878 in the wild since at least 7 Apr 2023, including in ransomware campaigns.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-27878/ (Markdown: https://insights.sbomify.com/CVE-2021-27878/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27878
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27878
- OSV: https://osv.dev/vulnerability/CVE-2021-27878

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-27878/
Summaries are generated and may contain mistakes; the official description above is the record.