CVE-2026-124737
Busybox: heap buffer overflow in the tftp client on fallback to the default block size
CVE-2026-124737 is a high vulnerability (CVSS 7.5) in Red Hat Enterprise Linux 6, published November 11, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.45%, the 39th percentile. No source names a fixed version.
- Severity
- 7.5 HighCVSS 3.1, CVE List
- Exploit chance
- 0.45%EPSS, 39th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
- No fix listedNo source names one
Description
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
Discussion
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
busyboxUbuntu:Pro:14.04:LTS | All versions, plus listed versions 1:1.20.0-8.1ubuntu11:1.20.0-9ubuntu11:1.20.0-9ubuntu21:1.21.0-1ubuntu11:1.21.0-1ubuntu1.41:1.21.0-1ubuntu1.4+esm1 | None known |
busyboxUbuntu:Pro:16.04:LTS | All versions, plus listed versions 1:1.22.0-15ubuntu11:1.22.0-15ubuntu1.41:1.22.0-15ubuntu1.4+esm11:1.22.0-15ubuntu1.4+esm2 | None known |
busyboxUbuntu:Pro:18.04:LTS | All versions, plus listed versions 1:1.22.0-19ubuntu21:1.27.2-1ubuntu31:1.27.2-1ubuntu41:1.27.2-2ubuntu21:1.27.2-2ubuntu3 Show 5 moreShow less1:1.27.2-2ubuntu3.11:1.27.2-2ubuntu3.21:1.27.2-2ubuntu3.31:1.27.2-2ubuntu3.41:1.27.2-2ubuntu3.4+esm1 | None known |
busyboxUbuntu:20.04:LTS | All versions, plus listed versions 1:1.30.1-4ubuntu41:1.30.1-4ubuntu51:1.30.1-4ubuntu61:1.30.1-4ubuntu6.11:1.30.1-4ubuntu6.21:1.30.1-4ubuntu6.31:1.30.1-4ubuntu6.41:1.30.1-4ubuntu6.5 | None known |
busyboxUbuntu:22.04:LTS | All versions, plus listed versions 1:1.30.1-6ubuntu31:1.30.1-7ubuntu11:1.30.1-7ubuntu21:1.30.1-7ubuntu31:1.30.1-7ubuntu3.1 | None known |
busyboxUbuntu:24.04:LTS | All versions, plus listed versions 1:1.36.1-3ubuntu11:1.36.1-6ubuntu11:1.36.1-6ubuntu31:1.36.1-6ubuntu3.1 | None known |
busyboxUbuntu:26.10 | All versions, plus listed versions 1:1.37.0-7ubuntu11:1.37.0-10.1ubuntu21:1.37.0-10.1ubuntu31:1.38.0-3ubuntu11:1.38.0-3ubuntu31:1.38.0-3ubuntu4 | None known |
busyboxUbuntu:26.04:LTS | All versions, plus listed versions 1:1.37.0-4ubuntu11:1.37.0-7ubuntu1 | None known |
What each source reports
CVE List Score used
Busybox: heap buffer overflow in the tftp client on fallback to the default block size
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.
- Record
CVE-2026-124737- 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 - Weakness
- CWE-787
- Updated
- 2026-11-11
EUVDEUVD-2026-123345
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.
- Record
EUVD-2026-123345- 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 - Updated
- 2026-11-11
GitHub AdvisoriesGHSA-r558-xpjx-65pf
A flaw was found in BusyBox. When the TFTP (Trivial File Transfer Protocol) client requests a...
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.
- Record
GHSA-r558-xpjx-65pf- 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 - Weakness
- CWE-787
- Updated
- 2026-11-11
NVD
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.
- Record
CVE-2026-124737- 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 - Weakness
- CWE-787
- Updated
- 2026-11-11
OSVUBUNTU-CVE-2026-124737
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.
- Record
UBUNTU-CVE-2026-124737- 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 - Updated
- 2026-11-13
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, references | OSV | |
| published | EUVD | |
| published | EUVD | |
| aliases, references | GitHub Advisories, NVD | |
| first indexed | CVE List, EUVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.