CVE-2026-88648

This flaw is rated Moderate by Red Hat Product Security. GnuTLS performs incomplete X.509 certificate validation, which allows an attacker who controls a subordinate Certificate Authority (CA) to bypass cross-domain Public Key Infrastructure (PKI) restrictions and issue unauthorized certificates for domains outside that CA's scope. Applications that use GnuTLS to validate certificates may accept such forged certificates as valid, enabling the attacker to impersonate trusted domains and intercept or tamper with TLS-protected communications, with high impact to confidentiality and integrity and no direct impact on availability. Exploitation is complex: it requires the attacker to already control a subordinate CA within the target's trust hierarchy and to be in a position to intercept or redirect the target's network connections. Affected Red Hat products include Red Hat Enterprise Linux 6 through 10 (including the mingw-gnutls variant), Red Hat Hardened Images, and Fedora, where GnuTLS is used for X.509 path validation; fixes for these affected products are being pursued through their respective product streams. The Red Hat CVSS 3.1 score for this flaw is 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N); the overall impact rating is Moderate because successful exploitation depends on control of a trusted subordinate CA and a network interception position.