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Advisories

U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()

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severity
high
date
Affecting

  • U-Boot <= 2026.04-rc3

  • An affected version range remains undefined

CWE
  • CWE-191 Integer Underflow (Wrap or Wraparound)
CVSS
8.7
CVSS V4 Vector
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
Credit
Kazuma Matsumoto, a security researcher at GMO Cybersecurity by IERAE, Inc.
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.

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