CVE-2022-33103 in Das U-Boot
Summary
by MITRE • 07/01/2022
Das U-Boot from v2020.10 to v2022.07-rc3 was discovered to contain an out-of-bounds write via the function sqfs_readdir().
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Analysis
by VulDB Data Team • 11/04/2025
The vulnerability CVE-2022-33103 represents a critical out-of-bounds write flaw within the Das U-Boot bootloader ecosystem affecting versions from v2020.10 through v2022.07-rc3. This issue resides within the sqfs_readdir() function which processes SquashFS filesystem operations, making it particularly dangerous in embedded systems where U-Boot serves as the primary bootloader and firmware interface. The vulnerability stems from inadequate bounds checking during directory traversal operations on SquashFS filesystems, creating potential for arbitrary code execution or system instability when malformed filesystem data is encountered during boot processes.
The technical implementation of this flaw occurs within the SquashFS filesystem parsing logic where the sqfs_readdir() function fails to properly validate array indices when reading directory entries. This allows an attacker to craft malicious SquashFS images that, when processed by the vulnerable U-Boot version, can cause memory corruption through buffer overflows. The out-of-bounds write vulnerability maps directly to CWE-787, which specifically addresses out-of-bounds write conditions in software implementations. The vulnerability is particularly concerning because U-Boot operates in privileged execution modes during system boot, meaning successful exploitation could lead to complete system compromise before normal operating system security mechanisms are active.
Operationally, this vulnerability impacts embedded devices, IoT systems, and embedded computing platforms that rely on U-Boot for their boot process and firmware management. Attackers could exploit this issue by placing maliciously crafted SquashFS images on boot media, potentially gaining control over the device before the operating system loads. The attack surface extends to any system where U-Boot processes filesystem data, including industrial control systems, network equipment, and automotive embedded systems. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary code during the boot process, and T1547.001 for registry run keys or startup folder, since compromised bootloaders can persistently modify system startup behavior.
Mitigation strategies should prioritize immediate firmware updates to versions beyond v2022.07-rc3 where the vulnerability has been patched. System administrators should implement strict firmware validation procedures and avoid loading untrusted filesystem images during boot processes. Additional protective measures include enabling memory protection features like stack canaries and address space layout randomization where supported, though these provide limited protection against bootloader-level exploits. Organizations should also consider implementing secure boot mechanisms that verify U-Boot integrity before execution, and establish monitoring procedures to detect unauthorized firmware modifications. The vulnerability demonstrates the critical importance of validating filesystem operations in bootloader environments, as these components represent the first line of defense in embedded system security architectures.