CVE-2026-29008 u-boot CVE debrief

Who should care

Organizations using U-Boot version through 2026.04-rc3 should be aware of this vulnerability and take necessary actions to mitigate the risk. This includes reviewing U-Boot deployments, assessing potential impact, and implementing compensating controls for exposed systems.

Technical summary

The vulnerability exists in the tcp_rx_state_machine() function in net/tcp.c of U-Boot. When the TCP_SYN_SENT handler calls tcp_rx_user_data() without invoking tcp_seg_in_wnd() validation, a negative payload_len is implicitly converted to a large unsigned integer and passed to memcpy() in store_block(). This causes an immediate crash that prevents device boot and may enable memory corruption when CONFIG_LMB is disabled. Affected product deployments should be reviewed for potential impact.

Defensive priority

High

Recommended defensive actions

• Inventory and assess U-Boot usage in your organization
• Check for and apply vendor patches or updates
• Implement compensating controls such as network monitoring and filtering
• Consider disabling CONFIG_LMB if not required
• Review relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-08T17:17:21.047Z and was last modified on 2026-07-10T18:01:31.563Z. The NVD entry is currently Awaiting Analysis. This vulnerability affects U-Boot versions through 2026.04-rc3. The vulnerability allows a network-adjacent attacker to crash the bootloader by sending a malformed TCP SYN+ACK packet. To verify, defenders should review official advisories and assess U-Boot usage in their organization.

Official resources