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.
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
< 2026.04CPE matchmatch criteria | cpe:2.3:a:denx:u-boot:*:*:*:*:*:*:*:* | ||
2026.04CPE matchmatch criteria | cpe:2.3:a:denx:u-boot:2026.04:rc1:*:*:*:*:*:* | ||
2026.04CPE matchmatch criteria | cpe:2.3:a:denx:u-boot:2026.04:rc2:*:*:*:*:*:* | ||
2026.04CPE matchmatch criteria | cpe:2.3:a:denx:u-boot:2026.04:rc3:*:*:*:*:*:* |
CVSS version used by this source: 4.0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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