U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()
41Vexday Risk Score
No sign of exploitation. It has a public proof of concept.
ssvc Attendcvss 8.7epss 0.6%
exploitation probability
0.6%top 56% of all CVEs
observed exploitation
nono source reports it
1 public exploit(s)
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.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Affected products
u-boot · u-bootpublic PoCs found — 1
cve_referencey637f9qq2x.com/posts/u-boot-tcp-nfs-vulns/unverified⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.