Cyber Resilience

CVE-2016-20021

Critical

Published: 12 January 2024

Published
12 January 2024
Modified
03 June 2025
KEV Added
Patch
CVSS Score v3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0004 11.9th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2016-20021 is a critical-severity Improper Verification of Cryptographic Signature (CWE-347) vulnerability in Gentoo Portage. Its CVSS base score is 9.8 (Critical).

Operationally, ranked at the 11.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

In Gentoo Portage before 3.0.47, there is missing PGP validation of executed code: the standalone emerge-webrsync downloads a .gpgsig file but does not perform signature verification. Unless emerge-webrsync is used, Portage is not vulnerable.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

gentoo
portage
≤ 3.0.47

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-347

Requires verification of digital signatures using organization-approved certificates before installation, directly preventing improper verification of cryptographic signatures.

addresses: CWE-347

Component authenticity commonly depends on cryptographic signatures; the control enforces proper verification of those signatures.

addresses: CWE-347

PKI certificates under an approved policy require cryptographic signature verification on issuance and validation.

addresses: CWE-347

Requires cryptographic signatures on authoritative data and support for verifying the chain of trust.

addresses: CWE-347

Mandates verification of cryptographic signatures (e.g., DNSSEC RRSIG) on resolution responses, addressing missing or bypassed signature checks.

addresses: CWE-347

Integrity tools commonly rely on cryptographic signatures whose improper validation this weakness covers.

addresses: CWE-347

Authenticity validation commonly relies on cryptographic signature or certificate checks that this control enforces.

References