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CVE-2026-29008

Denx U-boot integer overflow

7.5 HIGHPublic exploitEPSS 0.71%
  1. Published8 Jul 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Denx U-boot< 2026.04 · 2026.04

Remediation

Fixed in
Denx U-boot≥ 2026.04

References

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Frequently asked

Is CVE-2026-29008 being actively exploited?

CVE-2026-29008 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.71%.

How severe is CVE-2026-29008?

CVE-2026-29008 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.71% probability of exploitation.

Which products are affected by CVE-2026-29008?

Affected products include Denx U-boot.

How do I fix CVE-2026-29008?

Upgrade affected software to a fixed version, for example Denx U-boot 2026.04 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-29008 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.