---
id: "CVE-2026-121626"
kind: "vulnerability"
aliases: ["CVE-2026-121626"]
title: "GNU Gatekeeper: short probe packet causes heap over-read and possible crash"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["gnugk", "h323", "infrastructure", "self-hosted", "voip"]
not_affected_if: ["gnugk-5.16-or-later", "h460-24-disabled"]
published_at: "2026-11-03T18:17:58+00:00"
first_seen_at: "2026-11-03T18:22:10+00:00"
updated_at: "2026-11-03T18:22:37+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121626", "first_seen_at": "2026-11-03T18:22:10+00:00"}]
---

# GNU Gatekeeper: short probe packet causes heap over-read and possible crash

GNU Gatekeeper (gnugk) before 5.16 has an out-of-bounds read in its H.460.24 probing code, triggered by a short RTCP packet sent to the media port. A remote attacker can read past a heap allocation and possibly crash the gatekeeper.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed gnugk version against the fixed release (`gnugk --version` or the package manager's version query).
- Confirm whether H.460.24 probing is enabled in the gatekeeper configuration; unknown whether the sources name the exact setting.

## Fix

- GNU Gatekeeper: upgrade to `5.16` or later (per the sources' 'before 5.16' range).

## Timeline

- 2026-11-03T18:22:10+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121626

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/gnu-gatekeeper-before-5.16-out-of-bounds-read-in-h-460.24-rtcp-probe-handler
- [fix] Patch: github.com https://github.com/willamowius/gnugk/commit/160aa27344ecc9a443cccaa63e8d7fa95a766610
- [fix] Release notes: github.com https://github.com/willamowius/gnugk/releases/tag/v5_16

## From the sources

GNU Gatekeeper (gnugk) before 5.16 contains an out-of-bounds read vulnerability in H46024Socket::ReceivedProbePacket() that allows remote attackers to cause a heap over-read by sending short probe packets. Attackers can send a short application-defined RTCP packet to the media port during H.460.24 probing to read past the heap allocation and possibly crash the gatekeeper.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_