High 7.5Published Jul 8, 2026

CVE-2026-29008U-Boot 2026.04-rc3 Integer Underflow DoS via tcp_rx_state_machine()

Updated under an hour ago (Oct 26, 2026, 3:00 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-191
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Analyzed
Record last updated: Jul 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

u-boot u-boot u_boot:u_boot (from the name)	through 2026.04-rc3	CNA record
denx u-boot denx:u-boot	before 2026.04; 2026.04; 2026.04; 2026.04	NVD

References

References

https://y637f9qq2x.com/posts/u-boot-tcp-nfs-vulns/	technical-description, exploit, third-party-advisory
https://lists.denx.de/pipermail/u-boot/2026-May/617853.html	issue-tracking, mailing-list, third-party-advisory
https://u-boot.org/	product
https://www.vulncheck.com/advisories/u-boot-rc3-integer-underflow-dos-via-tcp-rx-state-machine	third-party-advisory, exploit

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.