Is CVE-2026-88647 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-88647 being exploited in the wild.

How severe is CVE-2026-88647?

Medium severity, with a CVSS score of 6.5, published 8 October 2026.

Is there a fix for CVE-2026-88647?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-88647 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-88647?

Check whether you run Gnutls at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-88647: GnuTLS hostname verification bypass via Common Name fallback

CVE-2026-88647 · Severity: medium · CVSS 6.5 · Published 2026-10-08

GnuTLS is a cryptographic library that validates TLS certificates to ensure secure communication. A flaw in version 3.8.13 allows attackers to bypass hostname verification by crafting certificates with malformed Subject Alternative Names, causing the library to fall back to accepting the Common Name even when it shouldn't. An attacker with certificate issuance capabilities could trick clients into accepting connections to the wrong server, enabling eavesdropping on encrypted communications.

Technologies: Gnutls. Vendors: Gnu.

Quick answers

Is CVE-2026-88647 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-88647 being exploited in the wild.
How severe is CVE-2026-88647?: Medium severity, with a CVSS score of 6.5, published 8 October 2026.
Which products and versions are affected?: Gnutls 3.8.13.
Is there a fix for CVE-2026-88647?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-88647 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-88647?: Check whether you run Gnutls at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is an improper certificate validation flaw (CWE-295) where GnuTLS fails to properly suppress Common Name fallback when a certificate contains unsupported or malformed SAN entries (specifically SRV otherName encoded as OCTET STRING instead of IA5String, or unsupported SAN types like URI). The vulnerable code path in gnutls_x509_othername_to_virtual() does not set the expected type when decoding fails, preventing the PRECLUDES_CN_FALLBACK macro from blocking CN matching. An attacker needs control over certificate issuance and must craft a certificate with a SAN containing an unsupported/malformed entry paired with an attacker-chosen CN matching the victim hostname; the client-side attack vector requires network access for TLS handshake interception.

Affected products

GNU GnuTLS 3.8.13

Timeline

2026-10-08: disclosed

References

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