CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HCVE-2026-124737 Busybox: heap buffer overflow in the tftp client on fallback to the default block size
High (7.5) in red hat. EPSS 0.5% estimated probability of exploitation activity in the next 30 days.
On this page
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.
Severity
- EPSS
- 0.5% estimated probability of exploitation activity in the next 30 days; 40th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-787 Out-of-bounds Write
- Published
- Modified
- Assigned by
- redhat (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
- red hat:red hat enterprise linux 6
- red hat:red hat hardened images
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 20.04:LTS, 22.04:LTS, 24.04:LTS and 5 more | busybox | no fix listed | UBUNTU-CVE-2026-124737 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.
Red Hat
Red Hat rates this Important.
Red Hat Product Security rates this vulnerability as having an Important severity because it allows a rogue network server to achieve remote code execution or terminate the client process without requiring prior authentication. BusyBox is predominantly deployed within lightweight container base images and recovery environments, where network file transfer operations are typically confined to administrative provisioning. While triggering the issue requires an active connection to an untrusted server using a non-default, reduced block size, the potential blast radius of arbitrary code execution justifies the Important rating over Moderate.
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.
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 6 | busybox | Affected | |
| Red Hat Hardened Images | busybox | Affected |
Contains Red Hat Security Data © Red Hat, Inc., licensed under CC BY 4.0. Source: https://access.redhat.com/security/data. Modified: reformatted. Red Hat's page for CVE-2026-124737.