{"id":"DEBIAN-CVE-2026-63794","details":"In the Linux kernel, the following vulnerability has been resolved:  KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path  In sev_dbg_crypt(), the per-iteration transfer length is bounded by the source page offset (PAGE_SIZE - s_off) but not by the destination page offset (PAGE_SIZE - d_off).  When d_off \u003e s_off, the encrypt path (__sev_dbg_encrypt_user) performs a read-modify-write using a single-page intermediate buffer (dst_tpage):    1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off & 15), 16)      before issuing the PSP command.  If len + (d_off & 15) \u003e PAGE_SIZE,      the PSP writes beyond the end of the 4096-byte dst_tpage allocation.    2. The subsequent memcpy()/copy_from_user() into      page_address(dst_tpage) + (d_off & 15) of 'len' bytes overflows      by up to 15 bytes under the same condition.  Trigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE - the PSP is instructed to write round_up(4097, 16) = 4112 bytes to a 4096-byte buffer.  Fix by also bounding len by (PAGE_SIZE - d_off), the same check that sev_send_update_data() already performs for its single-page guest region.   ==================================================================  BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd]  Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214   CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G     U  W           7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY  Tainted: [U]=USER, [W]=WARN  Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025  Call Trace:   \u003cTASK\u003e   dump_stack_lvl+0x54/0x70   print_report+0xbc/0x260   kasan_report+0xa2/0xd0   kasan_check_range+0x25f/0x2c0   __asan_memcpy+0x40/0x70   sev_dbg_crypt+0x993/0xd10 [kvm_amd]   sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd]   kvm_vm_ioctl+0x65d/0x6d0 [kvm]   __se_sys_ioctl+0xb2/0x100   do_syscall_64+0xe8/0x870   entry_SYSCALL_64_after_hwframe+0x4b/0x53   \u003c/TASK\u003e   The buggy address belongs to the physical page:  page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb  memcg:ff11000112827d82  flags: 0x1400000000000000(node=1|zone=1)  raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000  raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82  page dumped because: kasan: bad access detected   Memory state around the buggy address:   ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  \u003eff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc                     ^   ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc   ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc  ==================================================================  Disabling lock debugging due to kernel taint  [sean: add sample KASAN splat, Fixes, and stable@]","modified":"2026-09-29T13:04:13.462560715Z","published":"2026-07-19T12:16:51.757Z","upstream":["CVE-2026-63794"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-63794"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.177-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63794.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.95-1"}]}],"versions":["6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet 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