CVE-2026-43068

import os import subprocess import time # Conceptual PoC for CVE-2026-43068 # This script demonstrates how to trigger the ext4 allocation issue on a corrupted filesystem. # Requires root privileges and a test environment. def setup_test_image(): # Create a small ext4 image for testing img_file = "test_ext4.img" print(f"[*] Creating test image: {img_file}") subprocess.run(["dd", "if=/dev/zero", f"of={img_file}", "bs=1M", "count=50", "status=none"]) subprocess.run(["mkfs.ext4", "-F", img_file], stdout=subprocess.DEVNULL) return img_file def simulate_corruption(img_file): # Use debugfs to manipulate the block bitmap, simulating the corruption condition # This step aims to trigger the EXT4_MB_GRP_BBITMAP_CORRUPT state print(f"[*] Simulating block bitmap corruption on {img_file}...") # Note: Actual corruption commands depend on specific block group layouts # This is a placeholder for the logic that triggers the vulnerability pass def trigger_allocation_failure(img_file, mount_point): # Mount the image os.makedirs(mount_point, exist_ok=True) print(f"[*] Mounting image to {mount_point}") subprocess.run(["mount", "-o", "loop", img_file, mount_point], check=True) try: # Attempt to write data to trigger ext4_mb_find_by_goal # If the group is corrupted, this should log the error test_file = os.path.join(mount_point, "poc_test.dat") print(f"[*] Writing data to trigger allocation...") with open(test_file, "wb") as f: f.write(os.urandom(1024 * 1024 * 5)) # Check dmesg for the specific error message time.sleep(1) result = subprocess.run(["dmesg", "|", "grep", "Data will be lost"], shell=True) if result.returncode == 0: print("[+] Vulnerability triggered: 'Data will be lost' found in logs.") else: print("[-] Vulnerability not triggered or logs cleared.") except Exception as e: print(f"[!] An error occurred: {e}") finally: subprocess.run(["umount", mount_point]) print("[*] Cleanup complete.") if __name__ == "__main__": MOUNT_POINT = "/mnt/cve_test" img = setup_test_image() # simulate_corruption(img) # Requires specific implementation to corrupt bitmap # trigger_allocation_failure(img, MOUNT_POINT) print("[!] PoC structure generated. Manual bitmap corruption required to fully reproduce.")

{"cve": {"id": "CVE-2026-43068", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-05T16:16:16.053", "lastModified": "2026-05-20T23:09:44.863", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: avoid allocate block from corrupted group in ext4_mb_find_by_goal()\n\nThere's issue as follows:\n...\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2243 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2239 at logical offset 0 with max blocks 1 with error 117\nEXT4-fs (mmcblk0p1): This should not happen!! Data will be lost\n\nEXT4-fs (mmcblk0p1): error count since last fsck: 1\nEXT4-fs (mmcblk0p1): initial error at time 1765597433: ext4_mb_generate_buddy:760\nEXT4-fs (mmcblk0p1): last error at time 1765597433: ext4_mb_generate_buddy:760\n...\n\nAccording to the log analysis, blocks are always requested from the\ncorrupted block group. This may happen as follows:\next4_mb_find_by_goal\n ext4_mb_load_buddy\n ext4_mb_load_buddy_gfp\n ext4_mb_init_cache\n ext4_read_block_bitmap_nowait\n ext4_wait_block_bitmap\n ext4_validate_block_bitmap\n if (!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp))\n return -EFSCORRUPTED; // There's no logs.\n if (err)\n return err; // Will return error\next4_lock_group(ac->ac_sb, group);\n if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info))) // Unreachable\n goto out;\n\nAfter commit 9008a58e5dce (\"ext4: make the bitmap read routines return\nreal error codes\") merged, Commit 163a203ddb36 (\"ext4: mark block group\nas corrupt on block bitmap error\") is no real solution for allocating\nblocks from corrupted block groups. This is because if\n'EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)' is true, then\n'ext4_mb_load_buddy()' may return an error. This means that the block\nallocation will fail.\nTherefore, check block group if corrupted when ext4_mb_load_buddy()\nreturns error."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-401"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.12", "versionEndExcluding": "5.10.253", "matchCriteriaId": "0ECA9FA3-7D5A-47DF-96CD-50ED0F72C020"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.168", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.131", "matchCriteriaId": "CE6ED4D4-0046-4573-BFA9-D64143B6A89F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.80", "matchCriteriaId": "97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.21", "matchCriteriaId": "ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriter ... (truncated)