CVE-2025-21640: sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy
First published: Sun Jan 19 2025(Updated: )
In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: cookie_hmac_alg: 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.sctp_hmac_alg' is used.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | ||
| Linux Kernel | >=3.8<6.1.125 | |
| Linux Kernel | >=6.2<6.6.72 | |
| Linux Kernel | >=6.7<6.12.10 | |
| Linux Kernel | =6.13-rc1 | |
| Linux Kernel | =6.13-rc2 | |
| Linux Kernel | =6.13-rc3 | |
| Linux Kernel | =6.13-rc4 | |
| Linux Kernel | =6.13-rc5 | |
| Linux Kernel | =6.13-rc6 |
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Reference Links
- https://git.kernel.org/stable/c/1031462a944ba0fa83c25ab1111465f8345b5589
- https://git.kernel.org/stable/c/03ca51faba2b017bf6c90e139434c4117d0afcdc
- https://git.kernel.org/stable/c/86ddf8118123cb58a0fb8724cad6979c4069065b
- https://git.kernel.org/stable/c/3cd0659deb9c03535fd61839e91d4d4d3e51ac71
- https://git.kernel.org/stable/c/ad673e514b2793b8d5902f6ba6ab7e890dea23d5
- https://git.kernel.org/stable/c/f0bb3935470684306e4e04793a20ac4c4b08de0b
- https://git.kernel.org/stable/c/ea62dd1383913b5999f3d16ae99d411f41b528d4
Frequently Asked Questions
What is the severity of CVE-2025-21640?
CVE-2025-21640 is classified as a medium severity vulnerability in the Linux kernel.
How do I fix CVE-2025-21640?
To fix CVE-2025-21640, upgrade to the patched version of the Linux kernel provided by your distribution.
What systems are affected by CVE-2025-21640?
CVE-2025-21640 affects various versions of the Linux kernel.
What does CVE-2025-21640 exploit?
CVE-2025-21640 exploits an inconsistency related to the use of the 'net' structure by 'current' in the Linux kernel.
When was CVE-2025-21640 reported?
CVE-2025-21640 has been resolved in a recent commit in the ongoing development of the Linux kernel.
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