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CVE-2026-29008

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

Published: Jul 8, 2026Updated: Jul 22, 2026 Sources: CVE List NVDCWE-191
7.5HIGH
NVD MITRE
EPSS Score
0.6%
Top 56.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-191

Affected Products

denx
oss-project
u-bootEmbedded
DevTools & CI / build-test-tools
u-boot
u-boot

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Initial Access
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References

https://lists.denx.de/pipermail/u-boot/2026-May/617853.html
lists.denx.de
https://u-boot.org/
u-boot.org
https://www.vulncheck.com/advisories/u-boot-rc3-integer-underflow-dos-via-tcp-rx-state-machine
vulncheck.com
and 1 more references View all →

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