CVE-2025-32988 is a medium-severity double-free vulnerability discovered in GnuTLS, a widely used open-source TLS library. The flaw exists in the export logic for Subject Alternative Name (SAN) entries that contain an otherName field. Specifically, when the type-id Object Identifier (OID) in the otherName is invalid or malformed, GnuTLS incorrectly calls asn1_delete_structure() on an ASN.1 node it does not own. This results in a double-free condition when the parent function or caller subsequently attempts to free the same memory structure again. Double-free vulnerabilities can cause undefined behavior, including memory corruption, crashes, or potential exploitation for arbitrary code execution depending on the allocator behavior and environment. The vulnerability can be triggered remotely via public GnuTLS APIs without requiring authentication or user interaction, by presenting a specially crafted certificate containing malformed SAN otherName OIDs. The CVSS 3.1 score is 6.5 (medium), reflecting the network attack vector, high attack complexity, no privileges required, no user interaction, unchanged scope, no confidentiality impact, low integrity impact, and high availability impact. The vulnerability affects Red Hat Enterprise Linux 10 and potentially other distributions using the vulnerable GnuTLS versions. No known exploits are reported in the wild as of publication. The root cause is improper ownership handling of ASN.1 structures during certificate parsing and export, highlighting the importance of robust input validation and memory management in cryptographic libraries.

For European organizations, this vulnerability poses a risk primarily to the availability and integrity of TLS-based services relying on GnuTLS, such as web servers, mail servers, VPN gateways, and other network appliances. Exploitation could lead to denial of service through application crashes or memory corruption, potentially disrupting secure communications and business operations. While there is no direct confidentiality impact, service outages or integrity issues could indirectly affect data security and compliance with regulations like GDPR. Organizations using Red Hat Enterprise Linux 10 or other Linux distributions with vulnerable GnuTLS versions are particularly at risk. The medium severity and network exploitability mean attackers could remotely trigger the flaw without authentication, increasing the threat surface. Disruption of critical infrastructure or customer-facing services could have reputational and financial consequences. The absence of known exploits currently reduces immediate risk but does not eliminate the need for proactive mitigation.

1. Apply official patches from Red Hat or relevant Linux distributors as soon as they become available to address the double-free flaw in GnuTLS. 2. Temporarily mitigate risk by disabling or restricting services that rely on GnuTLS for TLS termination if patching is delayed. 3. Implement strict certificate validation policies to reject certificates with malformed or suspicious SAN otherName OIDs before processing. 4. Monitor logs and system behavior for crashes, memory errors, or unusual TLS handshake failures that could indicate exploitation attempts. 5. Employ runtime memory protection mechanisms such as AddressSanitizer or hardened allocators in development and testing environments to detect double-free conditions early. 6. Conduct regular vulnerability scanning and penetration testing focused on TLS implementations to identify potential exploitation paths. 7. Educate system administrators and security teams about this vulnerability to ensure timely response and patch management. 8. Consider network-level protections like Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) to detect and block malformed TLS handshake attempts targeting this flaw.