{"id":"CVE-2026-63794","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path\n\nIn sev_dbg_crypt(), the per-iteration transfer length is bounded by\nthe source page offset (PAGE_SIZE -…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path\n\nIn sev_dbg_crypt(), the per-iteration transfer length is bounded by\nthe source page offset (PAGE_SIZE -…","severity":"high","published":"2026-07-19","updated":"2026-07-19","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-63794","references":[{"url":"https://git.kernel.org/stable/c/2753a097d1fe24c4351c608048612c74108aa89f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/64f2449841ffc7d203183aa4c748c9c77951ecc5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/720949ed666f34ff28ffdfe1471a5861d1e41fdf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/78ee2d50185a037b3d2452a97f3dad69c3f7f389","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/889c2a9c59897ca912bf39df5bb92555a0a13df4","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9349b50f4b11f135fe73b56cb2c2c872d8bc71d7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e1a0fe288dee07b7da25a71e007c1ecd1080315b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f701ae476cb92a3a3d8844bb39bb63b4512684c8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63794.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-63794"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2502241"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63794"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63794"},{"url":"https://lore.kernel.org/linux-cve-announce/2026071959-CVE-2026-63794-b463@gregkh/T"},{"url":"https://access.redhat.com/errata/RHSA-2026:74438"},{"url":"https://access.redhat.com/errata/RHSA-2026:76738"},{"url":"https://access.redhat.com/errata/RHSA-2026:75747"},{"url":"https://access.redhat.com/errata/RHSA-2026:75746"}],"tags":["nvd","csaf","vex","red-hat"],"ingestedAt":"2026-07-19T23:34:10.623Z","epss":0.00142,"epssPercentile":0.03485,"vendor":"Red Hat","product":"Red Hat Enterprise Linux BaseOS (v. 9)","affected":["enterprise_linux 10","enterprise_linux 8","enterprise_linux 9","enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_9"],"patched":["enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_9"],"cvss":7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"vendor","cwe":["CWE-805"],"slug":"CVE-2026-63794","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path\n\nIn sev_dbg_crypt(), the per-iteration transfer length is bounded by\nthe source page offset (PAGE_SIZE - s_off) but not by the destination\npage offset (PAGE_SIZE - d_off).  When d_off > s_off, the encrypt\npath (__sev_dbg_encrypt_user) performs a read-modify-write using a\nsingle-page intermediate buffer (dst_tpage):\n\n  1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off & 15), 16)\n     before issuing the PSP command.  If len + (d_off & 15) > PAGE_SIZE,\n     the PSP writes beyond the end of the 4096-byte dst_tpage allocation.\n\n  2. The subsequent memcpy()/copy_from_user() into\n     page_address(dst_tpage) + (d_off & 15) of 'len' bytes overflows\n     by up to 15 bytes under the same condition.\n\nTrigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE -\nthe PSP is instructed to write round_up(4097, 16) = 4112 bytes to\na 4096-byte buffer.\n\nFix by also bounding len by (PAGE_SIZE - d_off), the same check that\nsev_send_update_data() already performs for its single-page guest\nregion.\n\n ==================================================================\n BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd]\n Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214\n\n CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G     U  W           7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY\n Tainted: [U]=USER, [W]=WARN\n Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025\n Call Trace:\n  <TASK>\n  dump_stack_lvl+0x54/0x70\n  print_report+0xbc/0x260\n  kasan_report+0xa2/0xd0\n  kasan_check_range+0x25f/0x2c0\n  __asan_memcpy+0x40/0x70\n  sev_dbg_crypt+0x993/0xd10 [kvm_amd]\n  sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd]\n  kvm_vm_ioctl+0x65d/0x6d0 [kvm]\n  __se_sys_ioctl+0xb2/0x100\n  do_syscall_64+0xe8/0x870\n  entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  </TASK>\n\n The buggy address belongs to the physical page:\n page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb\n memcg:ff11000112827d82\n flags: 0x1400000000000000(node=1|zone=1)\n raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000\n raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82\n page dumped because: kasan: bad access detected\n\n Memory state around the buggy address:\n  ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n  ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n >ff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n                    ^\n  ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n  ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n ==================================================================\n Disabling lock debugging due to kernel taint\n\n[sean: add sample KASAN splat, Fixes, and stable@]\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:74438** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-10-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:74438)\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63794.json)\n- **RHSA-2026:76738** · Red Hat · fixed in: 10Base-SMTV, Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Hidden (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), … · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76738)\n- **RHSA-2026:75747** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75747)\n- **RHSA-2026:75746** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75746)","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":38.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":214806,"id":"CVE-2026-63794","ts":1790927856346,"field":"cvss","old":null,"new":"7"},{"seq":214805,"id":"CVE-2026-63794","ts":1790927856346,"field":"severity","old":"none","new":"high"}]}