# CVE-2026-124737: Busybox: heap buffer overflow in the tftp client on fallback to the default block size

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

A flaw was found in BusyBox. When the TFTP (Trivial File Transfer Protocol) client requests a custom small block size and receives a standard response, it falls back to the default block size without resizing the allocated memory buffer. A malicious TFTP server can exploit this issue by sending standard-sized network packets during a transfer, causing a heap buffer overflow. This flaw allows an attacker to achieve arbitrary code execution or cause a Denial of Service (DoS) by crashing the application.

## Remediation

- workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 6 (busybox): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (busybox): 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: Not available

- SSVC: Not available

- Weaknesses: CWE-787

## Exploit evidence

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

## References

- https://access.redhat.com/security/cve/CVE-2026-124737 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2571607 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-124737 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2571607 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-124737; retrieved 2026-11-11; source updated 2026-11-11

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-124737; retrieved 2026-11-11; source updated 2026-11-11

Revision: 5297dd80e73c2c847268521b1836a1497404aae3cffcced78f15b04ebdec665c

Canonical: https://y2.dev/cve/CVE-2026-124737

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