CVE-2026-98065

Undergoing Analysis Undergoing Analysis - In Progress

Heap-based Buffer Overflow in Linux Kernel BPF

Publication date: 2026-09-25

Last updated on: 2026-10-03

Assigner: kernel.org

Description

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.

CVSS Scores

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Meta Information

Published

2026-09-25

Last Modified

2026-10-03

Generated

2026-10-16

AI Q&A

2026-09-25

EPSS Evaluated

2026-10-14

NVD

CVE-2026-98065

EUVD

EUVD-2026-86718

Affected Vendors & Products

Vendor	Product	Version / Range
linux_kernel	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a flaw in the BPF (Berkeley Packet Filter) subsystem where key-less BTF (BPF Type Format) is incorrectly allowed for hash maps. This leads to a kernel crash when reading such maps via bpffs due to a null pointer dereference in btf_type_show().

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF (Berkeley Packet Filter) implementation. Detection requires checking kernel logs for crashes related to bpf or hashtab operations. Use commands like 'dmesg | grep -i bpf' or 'journalctl -k | grep -i bpf' to search for kernel errors. If you suspect exploitation, monitor for unexpected system crashes or kernel panics.

Impact Analysis

This vulnerability can cause a system crash (kernel panic) when interacting with BPF hash maps that have key-less BTF. This may lead to denial of service, data corruption, or unauthorized access if exploited.

Compliance Impact

This vulnerability in the Linux kernel's BPF subsystem could potentially lead to memory corruption or crashes when processing key-less BTF data in hash maps. While not directly impacting GDPR or HIPAA compliance, such kernel vulnerabilities may affect system stability and data integrity, which are critical for maintaining compliance with these regulations.

Mitigation Strategies

Update your Linux kernel to the latest stable version that includes the fix for this issue. If immediate patching is not possible, disable BPF functionality if not required by your system. Monitor kernel security advisories for updates and apply them promptly.

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