{"id":"CVE-2026-29008","summary":"U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()","details":"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.","modified":"2026-08-12T03:51:10.830829264Z","published":"2026-07-08T16:14:41.613Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-191"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/29xxx/CVE-2026-29008.json"},"references":[{"type":"WEB","url":"https://u-boot.org/"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/29xxx/CVE-2026-29008.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-29008"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/u-boot-rc3-integer-underflow-dos-via-tcp-rx-state-machine"},{"type":"REPORT","url":"https://lists.denx.de/pipermail/u-boot/2026-May/617853.html"},{"type":"PACKAGE","url":"https://github.com/u-boot/u-boot"},{"type":"EVIDENCE","url":"https://y637f9qq2x.com/posts/u-boot-tcp-nfs-vulns/"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/u-boot/u-boot","events":[{"introduced":"0"},{"fixed":"88dc2788777babfd6322fa655df549a019aa1e69"},{"introduced":"aa4f687977a449686498236722ee5e93d8b39918"},{"last_affected":"4f70106beafe30df8b0528a3d8b2543cd48fe241"}],"database_specific":{"source":["CPE_RANGE","CPE_STRING"],"cpe":["cpe:2.3:a:denx:u-boot:*:*:*:*:*:*:*:*","cpe:2.3:a:denx:u-boot:2026.04:rc1:*:*:*:*:*:*","cpe:2.3:a:denx:u-boot:2026.04:rc2:*:*:*:*:*:*","cpe:2.3:a:denx:u-boot:2026.04:rc3:*:*:*:*:*:*"],"extracted_events":[{"introduced":"0"},{"fixed":"2026.04"},{"introduced":"2026.04-rc1"},{"last_affected":"2026.04-rc1"},{"introduced":"2026.04-rc2"},{"last_affected":"2026.04-rc2"},{"introduced":"2026.04-rc3"},{"last_affected":"2026.04-rc3"}]}}],"versions":["2026.04-rc1","2026.04-rc2","2026.04-rc3","v2026.04-rc4","v2026.04-rc5","v2026.04-rc3","v2026.04-rc2","v2026.04-rc1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-29008.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}