Network-filter bypass via incorrect tun/tap socket UID
Published Mar 27, 2023 · Updated Feb 24, 2025
Type confusion in the Linux Kernel allows local users with CAP_NET_ADMIN to bypass network filtering through tun/tap sockets. The tap_open and tun_chr_open paths pass embedded socket objects to sock_init_data, whose container lookup reads unrelated structure bytes and records UID 0 instead of the device owner's UID. A non-root local user must hold CAP_NET_ADMIN; affected routing or filtering logic can then treat that user's traffic as root-owned and permit traffic that policy intended to block.
Summary
What happened
Type confusion in the Linux Kernel allows local users with CAP_NET_ADMIN to bypass network filtering through tun/tap sockets. The tap_open and tun_chr_open paths pass embedded socket objects to sock_init_data, whose container lookup reads unrelated structure bytes and records UID 0 instead of the device owner's UID. A non-root local user must hold CAP_NET_ADMIN; affected routing or filtering logic can then treat that user's traffic as root-owned and permit traffic that policy intended to block.
The record
- CVE
- CVE-2023-1076
- Published
- Mar 27, 2023
- Updated
- Feb 24, 2025
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-791, CWE-843, T1562.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 27, 2023CVE publishedPublication date reported by the CVE source.
- Feb 24, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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- Affected versionversion=unknown
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What is affected?
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Your stack
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