SCTP authentication bypass via cross-namespace sysctl write
Published Jan 19, 2025 · Updated Aug 5, 2026
Improper namespace handling in affected Linux kernel versions allows local users to alter SCTP authentication or crash the kernel. The proc_sctp_do_hmac_alg handler reads current->nsproxy instead of deriving the namespace from the sysctl table, enabling a cross-namespace write or a NULL dereference during task exit. User-namespace access enables an unprivileged local user to disable host-wide SCTP cookie authentication; the acct(2) exit path requires accounting privileges and can cause an Oops or panic.
Summary
What happened
Improper namespace handling in affected Linux kernel versions allows local users to alter SCTP authentication or crash the kernel. The proc_sctp_do_hmac_alg handler reads current->nsproxy instead of deriving the namespace from the sysctl table, enabling a cross-namespace write or a NULL dereference during task exit. User-namespace access enables an unprivileged local user to disable host-wide SCTP cookie authentication; the acct(2) exit path requires accounting privileges and can cause an Oops or panic.
The record
- CVE
- CVE-2025-21640
- Published
- Jan 19, 2025
- Updated
- Aug 5, 2026
- Vendor
- Siemens
- Product
- SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
- Classifications
- CWE-476, T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 19, 2025CVE publishedPublication date reported by the CVE source.
- Aug 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=0 <*
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Attacks
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