# CVE-2026-121995: Gdb: gdb: stack buffer overflow in parse_tracepoint_definition via stale rs->buf tail

Status: published. Published: 2026-11-05. Updated: 2026-11-06.

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.

## Remediation

- workaround: There is no mitigation for this vulnerability. Users should only connect GDB to trusted debug targets.

--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to restrict GDB remote debugging sessions to trusted remote stubs and prevent connections to untrusted endpoints: upgrade to the corresponding fixed Red Hat builds, which apply the documented input check, closing crafted qTsP remote debug response following a longer qTfP response. Until patched, this is a concern on Linux systems running GDB remote debugging sessions connecting to remote debug targets, so Only initiate target remote debugging sessions to verified, trusted debug stubs and targets. As a compensating measure, Run SELinux in enforcing mode to confine GDB execution under mandatory access control and limit the blast radius of memory corruption. These controls limit blast radius and contain exploitation, but they do not fix the underlying stack buffer overflow defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium) (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (crash): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (crash): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (gcc-toolset-14-gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (gcc-toolset-15-gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (crash): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (gdb): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (gdb): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: redhat

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.29% as of 2026-11-06; percentile 22.03%

- SSVC: Not available

- Weaknesses: CWE-121

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-121995 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2565677 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-121995 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2565677 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-121995; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121995; retrieved 2026-11-06; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-121995; retrieved 2026-11-06; source updated Not reported

Revision: ff7284484ab794f02d40923f667737446bae94752759f6da16c51a120e40f709

Canonical: https://y2.dev/cve/CVE-2026-121995

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