CVE-2022-28734 in Grub2
Summary
by MITRE • 07/20/2023
Out-of-bounds write when handling split HTTP headers; When handling split HTTP headers, GRUB2 HTTP code accidentally moves its internal data buffer point by one position. This can lead to a out-of-bound write further when parsing the HTTP request, writing a NULL byte past the buffer. It's conceivable that an attacker controlled set of packets can lead to corruption of the GRUB2's internal memory metadata.
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Analysis
by VulDB Data Team • 05/19/2025
The vulnerability CVE-2022-28734 represents a critical out-of-bounds write condition within the GRUB2 bootloader's HTTP handling implementation. This flaw occurs specifically when processing split HTTP headers, where the bootloader's internal data buffer pointer is incorrectly incremented by one position during header parsing operations. The issue stems from improper boundary checking mechanisms within the HTTP request processing code, creating a scenario where memory corruption can occur beyond the allocated buffer boundaries. Such vulnerabilities are particularly dangerous in bootloader environments where memory corruption can lead to complete system compromise and bypass security mechanisms.
The technical implementation of this vulnerability involves the manipulation of GRUB2's internal buffer management during HTTP header parsing operations. When the bootloader encounters split HTTP headers, the code incorrectly advances its internal data pointer by one byte position, which then propagates through subsequent parsing operations. This misalignment causes the subsequent write operations to target memory locations beyond the intended buffer boundaries, resulting in a NULL byte being written past the allocated buffer limits. The flaw demonstrates poor memory management practices and inadequate input validation within the HTTP handling subsystem, creating opportunities for attackers to exploit memory corruption patterns that could be leveraged for further compromise.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential pathway for attackers to manipulate GRUB2's internal memory structures. The corruption of memory metadata within the bootloader can lead to arbitrary code execution, system instability, or complete system compromise during the boot process. Attackers could potentially craft malicious HTTP responses that, when processed by GRUB2, trigger the out-of-bounds write condition and subsequently corrupt critical bootloader components. This vulnerability aligns with CWE-787 Out-of-bounds Write, which specifically addresses buffer overflow conditions that write beyond allocated memory boundaries. The attack surface is particularly concerning given that GRUB2 serves as a critical boot component, making successful exploitation potentially devastating for system security.
Mitigation strategies for CVE-2022-28734 should focus on immediate patching of affected GRUB2 versions, as the vulnerability directly impacts the bootloader's core functionality. System administrators should prioritize updating to patched versions that correct the buffer pointer management during HTTP header parsing operations. Additionally, network-level controls such as HTTP traffic filtering and monitoring can help detect and prevent exploitation attempts. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1542.001 Rootkit, as memory corruption in bootloaders can create persistent backdoor access points. Organizations should implement comprehensive monitoring for unusual boot behavior or memory corruption patterns, and consider deploying secure boot mechanisms to prevent exploitation of such bootloader vulnerabilities. The fix typically involves correcting the buffer pointer increment logic and adding proper boundary checks to prevent the accidental advancement beyond valid memory boundaries during HTTP header processing operations.