---
id: CVE-2026-98065
title: |-
  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 …
summary: |-
  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 …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 451a84a3ad3c897c03181af433e7c98640730f1f <
    54098e3fe34ec190bc256b338b9a93c7e2dc9354
  - >-
    Linux >= 51a17f0ce19c4ee2a25cf16c93490d509b1ebb0a <
    fa047f2a025003f5654ebd76539f16a6ead0401a
  - >-
    Linux >= 1df97a7453eec80c1912c2d0360290a3970a7671 <
    7ca231252820c47aaec42a5db580db98f9b64724
  - >-
    Linux >= 1df97a7453eec80c1912c2d0360290a3970a7671 <
    0895a0c0734703be5532f3883c42db95615fd98b
  - Linux 7.0
published: '2026-09-25'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:18:27.217'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98065'
references:
  - url: 'https://git.kernel.org/stable/c/0895a0c0734703be5532f3883c42db95615fd98b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/54098e3fe34ec190bc256b338b9a93c7e2dc9354'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7ca231252820c47aaec42a5db580db98f9b64724'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fa047f2a025003f5654ebd76539f16a6ead0401a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98065.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-98065'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2541294'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-98065'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98065'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98065.mbox
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00168
epssPercentile: 0.05985
cvssSource: vendor
ingestedAt: '2026-09-25T11:06:38.842Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-29 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98065.json)