CVE-2026-98065: 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

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

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: ffffc9000399

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.17%, higher than 6% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

Weekly security brief

The flaws that hit local websites, every Friday.

One short email: what got exploited this week, which WordPress plugins broke, and what to check. Unsubscribe in one click.