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Fencer Vulns
medium 4.7

CVE-2021-3521 json

There is a flaw in RPM's signature functionality.

published 2022-08-22 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26837

cvss
4.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

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.

Patch / fix

  • rpm rpm 4.17.1
  • rpm Debian 14, Debian 13, Debian 12 4.18.0+dfsg-1

debian advisories DEBIAN-CVE-2021-3521

  • rpm RHEL 8 4.14.3-19.el8_5.2
  • rpm-cron RHEL 8 4.14.3-19.el8_5.2
  • rpm-libs RHEL 8 4.14.3-19.el8_5.2
  • rpm-sign RHEL 8 4.14.3-19.el8_5.2
  • rpm-build RHEL 8 4.14.3-19.el8_5.2
  • python3-rpm RHEL 8 4.14.3-19.el8_5.2
  • rpm-apidocs RHEL 8 4.14.3-19.el8_5.2
  • rpm-build-libs RHEL 8 4.14.3-19.el8_5.2

red hat advisories RHSA-2022:0634RHSA-2022:0368RHSA-2022:0254

  • rpm SLE Module for Development Tools 15 SP6, SLE Module for Development Tools 15 SP5, SLE Module for Basesystem 15 SP6 +14 more 4.14.3-150400.59.16.1
  • rpm-ndb SLE Module for Public Cloud 15 SP6, SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 +5 more 4.14.3-150400.59.16.1
  • python-rpm SLE Module for Python 3 15 SP6, SLE Module for Python 3 15 SP5, SLE Module for Basesystem 15 SP6 +12 more 4.14.3-150400.59.16.1

suse advisories SUSE-SU-2024:1557-2SUSE-SU-2024:1557-3SUSE-SU-2024:1557-1

  • rpm openSUSE Tumbleweed 4.17.1-1.1

opensuse advisories openSUSE-SU-2024:12245-1

  • rpm-build AlmaLinux 8 4.14.3-19.el8_5.2
  • rpm-plugin-fapolicyd AlmaLinux 8 4.14.3-19.el8_5.2

almalinux advisories ALSA-2022:0368

  • rpm Rocky Linux 8 4.14.3-19.el8_5.2

rocky linux advisories RLSA-2022:0368

  • rpm Alpine 3.24, Alpine 3.23, Alpine 3.22 +5 more 4.17.1-r0

alpine advisories ALPINE-CVE-2021-3521

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rpm CBL-Mariner 2.0 4.18.0-1

azure linux advisories AZL-10637

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3521 updated cvss 4.4

rpm: RPM does not require subkeys to have a valid binding signature

  • Red Hat Enterprise Linux 6 rpm, rpm-cron, rpm-libs, rpm-build, rpm-python, rpm-apidocs Red Hat Enterprise Linux 7 rpm, rpm-cron, rpm-libs, rpm-sign, rpm-build, rpm-python, +3 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) rpm-build 4.14.3-19.el8_5.2, rpm-plugin-fapolicyd 4.14.3-19.el8_5.2
    fixed: vendor fix RHSA-2022:0368
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) rpm-build 4.14.2-40.el8_2
    fixed: vendor fix RHSA-2022:0634
  • Red Hat Enterprise Linux AppStream EUS (v.8.4) rpm-build 4.14.3-14.el8_4.2, rpm-plugin-fapolicyd 4.14.3-14.el8_4.2
    fixed: vendor fix RHSA-2022:0254
  • Red Hat Enterprise Linux BaseOS (v. 8) rpm 4.14.3-19.el8_5.2, rpm-cron 4.14.3-19.el8_5.2, rpm-libs 4.14.3-19.el8_5.2, rpm-sign 4.14.3-19.el8_5.2, python3-rpm 4.14.3-19.el8_5.2, rpm-apidocs 4.14.3-19.el8_5.2, +6 more
    fixed: vendor fix RHSA-2022:0368
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.2) rpm 4.14.2-40.el8_2, rpm-cron 4.14.2-40.el8_2, rpm-libs 4.14.2-40.el8_2, rpm-sign 4.14.2-40.el8_2, python3-rpm 4.14.2-40.el8_2, rpm-apidocs 4.14.2-40.el8_2, +6 more
    fixed: vendor fix RHSA-2022:0634
  • Red Hat Enterprise Linux BaseOS EUS (v.8.4) rpm 4.14.3-14.el8_4.2, rpm-cron 4.14.3-14.el8_4.2, rpm-libs 4.14.3-14.el8_4.2, rpm-sign 4.14.3-14.el8_4.2, python3-rpm 4.14.3-14.el8_4.2, rpm-apidocs 4.14.3-14.el8_4.2, +6 more
    fixed: vendor fix RHSA-2022:0254
  • Red Hat Enterprise Linux 9 rpm, rpm-cron, rpm-libs, rpm-sign, rpm-build, python3-rpm, +9 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

Affected products

  • n/a RPM

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.