Integer overflow in Denx U-Boot
CVE-2026-29008
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.
EPSS: 0.006 (43.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Denx U-boot — versions 2026.04
- U-boot — versions 0
Weakness classification (CWE)
References
- disclosure@vulncheck.com (issue-tracking, Mailing List, Third Party Advisory)
- disclosure@vulncheck.com (Product, product)
- disclosure@vulncheck.com (Exploit, Third Party Advisory, third-party-advisory)
- disclosure@vulncheck.com (Exploit, technical-description, Third Party Advisory, exploit)
Frequently asked questions
- What is CVE-2026-29008?
- CVE-2026-29008 is a high-severity vulnerability in Denx U-Boot, classified under Integer Underflow. CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-29008?
- High severity. CVSS v3 base score is 7.5 out of 10.