CVE-2026-29008 U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()
A network-adjacent attacker can crash the U-Boot bootloader or potentially execute code by sending a malformed TCP packet that triggers an integer underflow.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-29008?
CVE-2026-29008 is a high-severity vulnerability in u-boot, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
U-Boot through 2026.04-rc3 contains an integer underflow vulnerability in the tcp_rx_state_machine() function (net/tcp.c) that allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet with a manipulated data offset field causing payload_len to become negative. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, the negative payload_len is implicitly converted to a large unsigned integer (e.g., 0xFFFFFFD8) and passed to memcpy() in store_block(), causing an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled.
Weakness: CWE-191
Which versions are affected by CVE-2026-29008?
It affects 1 product.
Products include Denx U-Boot.
How do I fix CVE-2026-29008?
No fix has been published for CVE-2026-29008 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-29008 being exploited?
There is no known exploitation of CVE-2026-29008 in the wild and no public exploit code.
Other vulnerabilities in u-boot
Sources
Also known as DEBIAN-CVE-2026-29008, GHSA-3qwj-q697-4ppr, UBUNTU-CVE-2026-29008.