CVE-2026-68162 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
sctp: avoid auth_enable sysctl UAF during netns teardown
proc_sctp_do_auth() updates the SCTP control socket after changing net.sctp.auth_enable. The handler gets the per-net SCTP state from ctl->data, so an already opened sysctl file can still target a network namespace while that namespace is being torn down.
SCTP previously registered its per-net sysctls from sctp_defaults_init(), while the control socket is created later from sctp_ctrlsock_init(). This exposed a window during initialization where auth_enable was writable before net->sctp.ctl_sock existed, and a teardown window where auth_enable stayed writable after inet_ctl_sock_destroy() had released the control socket.
Move the per-net SCTP sysctl registration into sctp_ctrlsock_init() after sctp_ctl_sock_init() succeeds, and unregister the sysctl table before destroying the control socket in sctp_ctrlsock_exit(). If sysctl registration fails after the control socket was created, destroy the control socket in the same init path.
Make sctp_sysctl_net_unregister() tolerate a missing header and clear the saved pointer so init-error and exit paths can safely share the unregister helper.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a use-after-free condition affecting the Stream Control Transmission Protocol implementation within the Linux kernel's networking stack. The issue arises from improper synchronization between sysctl registration and network namespace teardown processes, creating a window where references to destroyed network namespace resources remain accessible. The flaw specifically impacts the sctp auth_enable parameter handling during network namespace destruction phases.
The technical root cause stems from the timing mismatch in SCTP subsystem initialization and cleanup routines. During normal operation, the proc_sctp_do_auth() function modifies authentication enable settings through sysctl interfaces while referencing per-network SCTP state information stored in ctl->data. However, when a network namespace undergoes teardown, the control socket reference becomes invalid while existing sysctl file descriptors may still point to the now-destroyed namespace context.
The vulnerability manifests as a race condition between two distinct kernel subsystems: the network namespace management system that handles destruction of per-net resources and the sysctl framework that manages runtime configuration parameters. The original implementation registered per-net SCTP sysctls during sctp_defaults_init() before creating the control socket in sctp_ctrlsock_init(), establishing a temporal gap where the authentication enable parameter could be modified even after the underlying control socket had been released.
This flaw creates potential security implications through arbitrary code execution possibilities when malicious actors exploit the dangling pointer references. The vulnerability is classified under CWE-416 Use After Free, which specifically addresses situations where memory locations are accessed after they have been freed. The operational impact extends beyond simple resource management issues to potentially compromise system integrity and stability during network namespace operations.
The recommended mitigation strategy involves reordering the initialization sequence to ensure sysctl registration occurs only after successful control socket creation in sctp_ctrlsock_init(). This approach eliminates the temporal window where authentication parameters could be modified against destroyed resources. Additionally, proper cleanup procedures now unregister sysctl tables before destroying control sockets, preventing dangling references during teardown operations.
The fix implements defensive programming practices by ensuring that sctp_sysctl_net_unregister() can gracefully handle missing header information and clears saved pointers to prevent double-free conditions. This approach aligns with ATT&CK technique T1059.006 Command and Scripting Interpreter: Python, where proper resource management prevents exploitation of temporal vulnerabilities in system-level components. The solution follows established kernel security patterns for managing reference counting and cleanup sequences during subsystem initialization and destruction phases.
This vulnerability demonstrates the critical importance of proper synchronization between kernel subsystems during resource lifecycle management. The fix addresses not only the immediate use-after-free condition but also establishes robust error handling paths that prevent cascading failures during initialization and teardown operations. The implementation ensures that all resource management operations maintain consistency between sysctl interfaces and underlying network namespace structures, preventing unauthorized access to freed memory locations and maintaining system stability during concurrent network operations.
The mitigation approach effectively closes the security window identified in the original implementation by enforcing proper ordering of initialization steps and implementing defensive cleanup procedures. This solution prevents attackers from exploiting the temporal gap where authentication parameters remained writable against destroyed control socket references, thereby protecting against potential privilege escalation or denial-of-service scenarios that could arise from such memory corruption conditions.