CVE-2026-42784: Signature Bypass (CVSS 7.4)

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.

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CVSS v3.1 Score

7.4

HIGH

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

Weakness Type (CWE)

CWE-347 CWE-347

References

Other References

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

Frequently Asked Questions

What is CVE-2026-42784? +

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. It has a CVSS v3.1 base score of 7.4 (HIGH).

How severe is CVE-2026-42784? +

CVE-2026-42784 has a CVSS v3.1 score of 7.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

How do I check if I'm vulnerable to CVE-2026-42784? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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