---
id: "CVE-2026-121625"
kind: "vulnerability"
aliases: ["CVE-2026-121625"]
title: "GNU Gatekeeper: malformed RTCP packet reads heap memory and can crash gatekeeper"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["gnugk", "h323", "runtime", "self-hosted", "voip"]
not_affected_if: ["enablertcpstats-disabled", "no-h323-proxy"]
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-2026-121625", "first_seen_at": "2026-11-03T18:22:10+00:00"}]
---

# GNU Gatekeeper: malformed RTCP packet reads heap memory and can crash gatekeeper

GNU Gatekeeper (gnugk) before 5.16 has an out-of-bounds read in ParseRTCP() that lets a remote RTP peer read heap memory past received packets. A crafted RTCP SDES packet without a NUL byte can 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 `5.16`.
- Check whether `EnableRTCPStats` is enabled in the gatekeeper configuration; the sources say the issue needs it on.

## Fix

- GNU Gatekeeper `5.16` or later (the sources name a patch and release notes for the fix; exact range not stated).

## Timeline

- 2026-11-03T18:22:10+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121625

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/gnu-gatekeeper-before-5.16-out-of-bounds-read-via-rtcp-sdes-parsing
- [fix] Patch: github.com https://github.com/willamowius/gnugk/commit/e8939d03b0b2ef46e356f3144a6ee14f2920b777
- [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 ParseRTCP() in ProxyChannel.cxx that allows remote RTP peers to read heap memory past received packets. Attackers can send RTCP SDES items lacking a NUL byte to the media proxy port during proxied H.323 calls with EnableRTCPStats enabled, crashing 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_