---
id: "CVE-2026-121997"
kind: "vulnerability"
aliases: ["CVE-2026-121997"]
title: "gdbserver: heap overflow in QTDPsrc packet lets remote attacker run code"
severity: "high"
cvss: 8.1
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "gdb", "fixed": [], "affected": "unknown versions; gdbserver shipped with RHEL", "ecosystem": "redhat"}]
ecosystems: []
tags: ["debugging", "embedded", "gdb", "gdbserver", "remote-debugging", "rhel", "runtime"]
not_affected_if: ["gdbserver-not-installed", "local-only-debugging", "loopback-only", "no-gdbserver"]
published_at: "2026-11-05T17:18:01+00:00"
first_seen_at: "2026-11-05T17:40:04+00:00"
updated_at: "2026-11-05T17:44:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121997", "first_seen_at": "2026-11-05T17:40:04+00:00"}, {"source": "analyst", "url": "https://access.redhat.com/security/cve/CVE-2026-121997", "first_seen_at": "2026-11-05T17:44:02+00:00", "cites": ["https://access.redhat.com/security/cve/CVE-2026-121997"]}]
exploit_sources: []
---

# gdbserver: heap overflow in QTDPsrc packet lets remote attacker run code

A heap buffer overflow in gdbserver's QTDPsrc packet handler happens when a packet's declared source length does not match the real data length, so hex2bin writes past the allocated buffer. An unauthenticated remote attacker can get native code execution inside the gdbserver process.

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

## Affected

- redhat:gdb affected unknown versions; gdbserver shipped with RHEL fixed no fixed version listed

## How to check

Check whether gdbserver is installed (RHEL: rpm -q gdb-gdbserver gdb) and whether it listens on a network port (ss -ltnp | grep gdbserver). Any gdbserver reachable over the network is exposed; gdbserver has no authentication. Fixed version: unknown, Red Hat has not published one on its CVE page.

## Timeline

- 2026-11-05T17:40:04+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121997
- 2026-11-05T17:44:02+00:00 analyst https://access.redhat.com/security/cve/CVE-2026-121997 — Red Hat CVE page read (only primary found; NVD page empty, no upstream GDB advisory/patch found, GDB 18.1 news doesn't mention it). Red Hat lists no fixed version and says no mitigation; fix status unknown. Red Hat scores AC:H 8.1, notes dispute for 9.8. No exploitation or PoC seen.

## Documents

- [advisory] Red Hat CVE-2026-121997 https://access.redhat.com/security/cve/CVE-2026-121997

## From the sources

A heap buffer overflow in gdbserver's QTDPsrc packet handler allows an unauthenticated remote attacker to achieve native code execution in the gdbserver process. The vulnerability results from a mismatch between a packet's declared source length and the actual data length, causing hex2bin to write beyond the allocated heap buffer.

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