{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-53360", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-06-09T07:44:35.400Z", "datePublished": "2026-07-04T11:53:58.657Z", "dateUpdated": "2026-08-05T12:35:09.892Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:35:09.892Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use\n\nAs per the GHCB spec, when using GHCB v2+ require the software scratch area\nto reside in the GHCB's shared buffer. Note, things like Page State Change\n(PSC) requests _rely_ on this behavior, as the guest can't provide a length\nwhen making the request, i.e. the size of the guest payload is bounded by\nthe size of the shared buffer.\n\nFailure to force usage of the GHCB, and a slew of other flaws, lets a\nmalicious SNP guest corrupt host kernel heap memory, and leak host heap\nlayout information.\n\nsetup_vmgexit_scratch() allocates a buffer via kvzalloc(exit_info_2),\nwhere exit_info_2 is guest-controlled. With exit_info_2=24, this yields\na 24-byte allocation in kmalloc-cg-32 (32-byte slab objects). The buffer\nholds an 8-byte psc_hdr followed by 8-byte psc_entry structs, so only\nentries[0] and entries[1] are in-bounds.\n\nsnp_begin_psc() validates end_entry against VMGEXIT_PSC_MAX_COUNT (253)\nbut NOT against the actual buffer size:\n\n idx_end = hdr->end_entry;\n\n if (idx_end >= VMGEXIT_PSC_MAX_COUNT) { // checks 253, not buffer\n snp_complete_psc(svm, ...);\n return 1;\n }\n\n for (idx = idx_start; idx <= idx_end; idx++) {\n entry_start = entries[idx]; // OOB when idx >= 2\n\nThe guest sets end_entry=10+, causing the host to iterate entries[2+]\nwhich are OOB into adjacent slab objects. For each OOB entry:\n\n - The host reads 8 bytes (OOB READ / info leak oracle)\n - If the data passes PSC validation, __snp_complete_one_psc() writes\n cur_page = 1 or 512 into the entry (OOB WRITE, sev.c:3806)\n - If validation fails, the error response reveals whether adjacent\n memory is zero vs non-zero (information disclosure to guest)\n\nThe guest controls allocation size (exit_info_2), entry range\n(cur_entry/end_entry), and can fire unlimited VMGEXITs to repeatedly\nhit different slab positions.\n\nBy exploiting the variety of bugs, a malicious SEV-SNP guest can:\n - OOB read adjacent kmalloc-cg-32 objects (heap layout disclosure)\n - OOB write cur_page bits into adjacent objects (heap corruption)\n - Trigger use-after-free conditions across VMGEXITs\n\nE.g. with KASAN enabled, a single insmod of the PoC guest module\nproduces 73 KASAN reports:\n\n BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x126/0x890\n Read of size 8 at addr ffff888219ffb5e0 by task qemu-system-x86/2199\n\n BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x468/0x890\n Write of size 8 at addr ffff888351566648 by task qemu-system-x86/2199\n\n The buggy address belongs to the object at ffff888XXXXXXXXX\n which belongs to the cache kmalloc-cg-32 of size 32\n The buggy address is located N bytes to the right of\n allocated 32-byte region [ffff888XXXXXXXXX, ffff888XXXXXXXXX)\n\n Breakdown:\n 62 slab-out-of-bounds (reads + writes past allocation)\n 7 slab-use-after-free\n 4 use-after-free\n\nAll credit to Stan for the wonderful description and reproducer!\n\n[sean: write changelog]" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable path is reached by running a SEV-SNP vCPU through KVM and issuing a guest-controlled VMGEXIT PSC request, not by remote packets or adjacent/physical access.\nAC:L - The guest directly controls the scratch pointer/length and PSC entry bounds, and can repeatedly issue malformed VMGEXITs without needing external races or rare timing conditions.\nPR:L - Exploitation requires the ability to run or control a SEV-SNP guest/KVM vCPU, which is a low-privilege local or tenant capability rather than real host root in the init namespace.\nUI:N - Once the attacker controls the malicious guest or VM process, no additional victim action is required to trigger the VMGEXIT handling path.\nS:C - The bug lets a malicious guest corrupt and disclose host kernel heap memory, crossing the guest-to-host virtualization security boundary.\nC:H - The OOB reads and error oracle leak adjacent host heap contents/layout, and the associated memory corruption/UAF behavior is sufficient to treat confidentiality impact as high.\nI:H - The vulnerable path performs OOB writes into adjacent host slab objects and can trigger UAF conditions, making host kernel memory corruption and potential control-flow compromise defensible.\nA:H - The bug produces host kernel slab OOB writes/reads and UAF reports and can crash or destabilize the host kernel, giving high availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/x86/kvm/svm/sev.c" ], "versions": [ { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "lessThan": "bf9ba093fbb83c0c9a3dedd50efec29424eca2fc", "status": "affected", "versionType": "git" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "lessThan": "c9b4198fbc6ed99a9da4bee9f74bb730f926c9ae", "status": "affected", "versionType": "git" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "lessThan": "b328ede59ac34e7998e1eee5e5f0cc26c2a91846", "status": "affected", "versionType": "git" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "lessThan": "db3f2195d29344a3cf1e9dd9ab7f21ced7308cf7", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "arch/x86/kvm/svm/sev.c" ], "versions": [ { "version": "6.10", "status": "affected" }, { "version": "0", "lessThan": "6.10", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/bf9ba093fbb83c0c9a3dedd50efec29424eca2fc" }, { "url": "https://git.kernel.org/stable/c/c9b4198fbc6ed99a9da4bee9f74bb730f926c9ae" }, { "url": "https://git.kernel.org/stable/c/b328ede59ac34e7998e1eee5e5f0cc26c2a91846" }, { "url": "https://git.kernel.org/stable/c/db3f2195d29344a3cf1e9dd9ab7f21ced7308cf7" } ], "title": "KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use", "x_generator": { "engine": "bippy-1.2.0" } } } }