CVE-2026-74222 in U-Boot
Summary
by MITRE • 09/30/2026
U-Boot before 2026.10-rc5 contains a use-after-free vulnerability in the httpc_recv_cb() function within the lwIP wget implementation. When HTTP data storage fails, the callback frees the connection PCB but returns ERR_BUF instead of ERR_ABRT, causing the TCP input path to access released memory and crash the bootloader.
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Analysis
by VulDB Data Team • 09/30/2026
The identified security flaw resides in the Universal Boot Loader (U-Boot) software stack prior to version 2026.10-rc5, specifically within the network initialization component that utilizes the lwIP protocol suite for HTTP client operations. This vulnerability is classified as a use-after-free error, which corresponds to CWE-416 in the Common Weakness Enumeration taxonomy. The issue manifests during the execution of the httpc_recv_cb callback function, which handles incoming data packets from an HTTP server. Under normal operational conditions, this routine processes received bytes and manages connection state transitions. However, a critical logic error occurs when the system attempts to store incoming HTTP data but encounters a failure condition, such as insufficient buffer space or memory allocation errors.
In this specific failure scenario, the code incorrectly proceeds to free the Protocol Control Block (PCB) associated with the TCP connection immediately after detecting the storage failure. This deallocation releases the memory resources allocated for managing the socket state back to the system heap. Crucially, despite freeing these critical structures, the function returns an ERR_BUF error code rather than ERR_ABRT or another abortive status that would signal a hard termination of the connection handling process. This discrepancy creates a dangerous race condition within the TCP input path of the lwIP stack. The higher-level network processing logic interprets the return value as a recoverable buffer issue and continues to attempt operations on the now-dereferenced PCB pointer, leading directly to memory corruption or a system crash.
The operational impact of this vulnerability is severe for embedded systems relying on U-Boot for remote booting or firmware updates via HTTP. An attacker with network access can trigger this condition by sending malformed HTTP responses that cause data storage failures during the download phase. This results in a denial-of-service attack against the bootloader, causing the device to hang or reboot unpredictably before reaching the operating system stage. Such instability compromises the availability of critical infrastructure and embedded devices, potentially preventing them from booting into their intended operational state. From an adversary perspective, this aligns with ATT&CK technique T1499, Endpoint Denial of Service, as it disrupts the primary function of the device by crashing its foundational software layer.
Mitigation strategies primarily involve upgrading to U-Boot version 2026.10-rc5 or later, where the logic error in httpc_recv_cb has been corrected to ensure proper resource management and appropriate return codes upon failure. For systems that cannot be immediately updated, network segmentation policies should be enforced to restrict HTTP access from untrusted networks during boot processes. Additionally, implementing strict input validation on any custom bootloader modifications can help prevent exploitation of similar memory management flaws in related protocol handlers. Security teams should also monitor for abnormal reboot patterns or boot failures associated with network-dependent initialization sequences as indicators of potential exploitation attempts targeting this specific weakness.