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Vulnerability record · CVE-2026-42784 · published 16 September 2026

CVE-2026-42784: Improper verification of cryptographic signature vulnerability

A flaw was found in sequoia-openpgp. The library incorrectly infers key flags for older certificates when a key flags subpacket is missing, leading to a discrepancy in how key capabilities are viewed. This key flag confusion allows an attacker to bypass the back-signature check. Consequently, an attacker can illegitimately bind an arbitrary subkey to their own certificate and forge signatures, completely compromising cryptographic integrity.

7.4 CVSS 3.1 High EPSS 0.20% · top 91.1% CWE-347 · Improper verification of cryptographic signature Awaiting Analysis
7.4CVSS 3.1 base score
0.20%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
23 Sep 2026Last modified by NVD

Description

A flaw was found in sequoia-openpgp. The library incorrectly infers key flags for older certificates when a key flags subpacket is missing, leading to a discrepancy in how key capabilities are viewed. This key flag confusion allows an attacker to bypass the back-signature check. Consequently, an attacker can illegitimately bind an arbitrary subkey to their own certificate and forge signatures, completely compromising cryptographic integrity.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N

References

LinkTags
https://access.redhat.com/errata/RHSA-2026:42902
https://access.redhat.com/security/cve/CVE-2026-42784
https://bugzilla.redhat.com/show_bug.cgi?id=2464122

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Source: NIST National Vulnerability Database (record CVE-2026-42784), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.