CVE-2026-98065

Status: UPDATED  |  Advisory ID: CVE-2026-98065

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reject key-less BTF for hash maps

map_check_btf() allows a key-less BTF (btf_key_type_id == 0) only for

maps that have a ->map_check_btf callback, and leaves the actual

decision to that callback. Hash maps used to have no ->map_check_btf,

so a key-less BTF was rejected outright.

That changed when htab and rhtab gained a ->map_check_btf to register a

dtor - htab in commit 1df97a7453ee ("bpf: Register dtor for freeing

special fields") and rhtab in commit 6905f8601298 ("bpf: Allow special

fields in resizable hashtab"). Neither looks at the key, so a key-less

hash map now passes map_check_btf() and gets created. Reading it back

through bpffs feeds the key type_id 0 into btf_type_seq_show();

btf_type_by_id() returns the void type, kind_ops[BTF_KIND_UNKN] is NULL,

and btf_type_show() dereferences it:

RIP: 0010:btf_type_show+0x223/0x2e0 kernel/bpf/btf.c:8232

RSP: 0018:ffffc9000399f868 EFLAGS: 00010206

RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000

RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000028

RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000

R10: ffffc9000399f970 R11: 0000000000000001 R12: ffffffff9b96b140

R13: ffffc9000399f8e0 R14: ffff88803d393c00 R15: 0000000000000003

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000200000000000 CR3: 000000003d213000 CR4: 0000000000352ef0

DR0: 0000000039ae8f55 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

btf_type_seq_show_flags+0xca/0x120 kernel/bpf/btf.c:8250

htab_map_seq_show_elem+0x12e/0x350 kernel/bpf/hashtab.c:1669

map_seq_show+0x13d/0x1e0 kernel/bpf/inode.c:293

traverse.part.0.constprop.0+0x107/0x650 fs/seq_file.c:112

traverse fs/seq_file.c:99 [inline]

seq_read_iter+0x93f/0x1270 fs/seq_file.c:196

seq_read+0x344/0x4d0 fs/seq_file.c:163

vfs_read+0x1e4/0xb40 fs/read_write.c:572

ksys_pread64 fs/read_write.c:764 [inline]

__do_sys_pread64 fs/read_write.c:772 [inline]

__se_sys_pread64 fs/read_write.c:769 [inline]

__x64_sys_pread64+0x1eb/0x250 fs/read_write.c:769

do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]

do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84

entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reject a key-less BTF in htab_map_check_btf() and rhtab_map_check_btf(),

restoring the previous behavior. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References