{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-53360", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-53360", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-07-04T11:53:58.657Z", "updatedAt": "2026-10-19T20:07:44.426Z", "importedAt": "2026-10-24T01:58:20.586Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use", "summary": "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]", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "status": "affected", "versionType": "git", "lessThan": "bf9ba093fbb83c0c9a3dedd50efec29424eca2fc" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "status": "affected", "versionType": "git", "lessThan": "c9b4198fbc6ed99a9da4bee9f74bb730f926c9ae" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "status": "affected", "versionType": "git", "lessThan": "b328ede59ac34e7998e1eee5e5f0cc26c2a91846" }, { "version": "4af663c2f64a8d252e690c60cf8b8abf22dc2951", "status": "affected", "versionType": "git", "lessThan": "db3f2195d29344a3cf1e9dd9ab7f21ced7308cf7" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "6.10", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "6.10" }, { "version": "6.12.93", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.35", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.0.12", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.0.*" }, { "version": "7.1", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }