# CVE-2021-47010: linux: In the Linux kernel, the following vulnerability has been resolved:  net: Only allow init netns to set default tcp co...

CVE-2021-47010 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47010, released February 28, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47010
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 28, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  net: Only allow init netns to set default tcp cong to a restricted algo  tcp_set_default_congestion_control() is netns-safe in that it writes to &net->ipv4.tcp_congestion_control, but it also sets ca->flags |= TCP_CONG_NON_RESTRICTED which is not namespaced. This has the unintended side-effect of changing the global net.ipv4.tcp_allowed_congestion_control sysctl, despite the fact that it is read-only: 97684f0970f6 ("net: Make tcp_allowed_congestion_control readonly in non-init netns")  Resolve this netns "leak" by only allowing the init netns to set the default algorithm to one that is restricted. This restriction could be removed if tcp_allowed_congestion_control were namespace-ified in the future.  This bug was uncovered with https://github.com/JonathonReinhart/linux-netns-sysctl-verify

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.10.38-1 | [DEBIAN-CVE-2021-47010](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47010.md) | Feb 28, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.10.38-1 | [DEBIAN-CVE-2021-47010](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47010.md) | Feb 28, 2024 |
| Linux | linux Debian 14 | 5.10.38-1 | [DEBIAN-CVE-2021-47010](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47010.md) | Feb 28, 2024 |

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