---
title: "CVE-2026-88647: GnuTLS - Authentication Bypass"
description: "GnuTLS 3.8.13 contains a hostname verification bypass caused by improper Common Name fallback mechanism handling, letting attackers eavesdrop on communications via crafted certificates, exploit requires crafted certificate."
url: https://panop.io/threat-heartbeat/CVE-2026-88647/
---

# CVE-2026-88647 GnuTLS - Authentication Bypass

GnuTLS 3.8.13 contains a hostname verification bypass caused by improper Common Name fallback mechanism handling, letting attackers eavesdrop on communications via crafted certificates, exploit requires crafted certificate.

CVSS base score 9.1 /10

Critical

CISA KEV

Not listed

Public exploit

None known

EPSS

0.21% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-88647)

## Details

Type

Authentication Bypass

Impact

Man In The Middle, Information Disclosure

CVSS vector

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

Published

8 October 2026

Updated

15 October 2026

Weakness

[CWE-297](https://cwe.mitre.org/data/definitions/297.html)

## Vendor fix

Update to the latest version of GnuTLS.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-88647](https://nvd.nist.gov/vuln/detail/CVE-2026-88647)
- [https://gist.github.com/lkloliver/f98ec3de1a871fdfc02b70b8b9ba7642](https://gist.github.com/lkloliver/f98ec3de1a871fdfc02b70b8b9ba7642)
- [https://gitlab.com/gnutls/gnutls/-/issues/1802](https://gitlab.com/gnutls/gnutls/-/issues/1802)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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