CVE-2022-50306 in Linux
Summary
by MITRE • 09/15/2025
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix potential out of bound read in ext4_fc_replay_scan()
For scan loop must ensure that at least EXT4_FC_TAG_BASE_LEN space. If remain space less than EXT4_FC_TAG_BASE_LEN which will lead to out of bound read when mounting corrupt file system image. ADD_RANGE/HEAD/TAIL is needed to add extra check when do journal scan, as this three tags will read data during scan, tag length couldn't less than data length which will read.
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Analysis
by VulDB Data Team • 01/10/2026
The vulnerability identified as CVE-2022-50306 represents a critical out-of-bounds read condition within the Linux kernel's ext4 file system implementation. This flaw specifically affects the ext4_fc_replay_scan() function which handles journal replay operations during file system mounting. The issue arises from insufficient validation of available buffer space during the scanning process, creating a scenario where maliciously crafted file system images could trigger unauthorized memory access patterns.
The technical root cause stems from inadequate boundary checking in the journal scanning loop where the system assumes a minimum buffer space of EXT4_FC_TAG_BASE_LEN bytes for processing file system tags. When the remaining buffer space falls below this threshold, the code proceeds to read beyond allocated memory boundaries, potentially exposing sensitive kernel memory contents or causing system instability. This vulnerability directly maps to CWE-129 Input Validation and CWE-787 Out-of-bounds Read, both of which are classified as high-risk issues in the Common Weakness Enumeration framework.
During normal file system operations, when the ext4 kernel module attempts to mount a corrupted or maliciously crafted file system image, the scanning process iterates through journal entries to reconstruct file system state. The flaw becomes apparent when processing ADD_RANGE, HEAD, and TAIL tags which require additional data reading operations beyond the basic tag structure. These specific tag types cannot proceed without sufficient data length validation, as they attempt to read actual content data from the journal stream, making the boundary check failure particularly dangerous during mount operations.
The operational impact of this vulnerability extends beyond simple memory corruption, as it could potentially enable privilege escalation attacks or denial-of-service conditions. Attackers could craft malicious file system images that, when mounted, trigger the out-of-bounds read condition and potentially expose kernel memory layout information. This information could be leveraged by adversaries to develop more sophisticated attacks targeting the kernel's memory management subsystem. The vulnerability affects systems running Linux kernel versions where the ext4 file system is implemented, particularly those with journal replay functionality enabled.
Mitigation strategies should prioritize immediate kernel updates to versions containing the patched ext4 implementation, which includes enhanced boundary validation for journal scanning operations. System administrators should also implement monitoring solutions to detect suspicious file system mounting operations and consider deploying kernel hardening configurations such as stack canaries and address space layout randomization. The fix ensures that all journal tag processing operations validate sufficient buffer space before attempting to read data, preventing the out-of-bounds access condition while maintaining proper file system recovery functionality. Organizations should also review their file system image validation processes and implement strict integrity checking mechanisms for any external storage media that may be mounted on affected systems, aligning with ATT&CK technique T1070.004 Indicator Removal on Host to prevent exploitation through corrupted image attacks.