CVE-2026-23286
Received Received - Intake
Null Pointer Dereference in Linux ATM LANE Module Causes Crash

Publication date: 2026-03-25

Last updated on: 2026-04-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: atm: lec: fix null-ptr-deref in lec_arp_clear_vccs syzkaller reported a null-ptr-deref in lec_arp_clear_vccs(). This issue can be easily reproduced using the syzkaller reproducer. In the ATM LANE (LAN Emulation) module, the same atm_vcc can be shared by multiple lec_arp_table entries (e.g., via entry->vcc or entry->recv_vcc). When the underlying VCC is closed, lec_vcc_close() iterates over all ARP entries and calls lec_arp_clear_vccs() for each matched entry. For example, when lec_vcc_close() iterates through the hlists in priv->lec_arp_empty_ones or other ARP tables: 1. In the first iteration, for the first matched ARP entry sharing the VCC, lec_arp_clear_vccs() frees the associated vpriv (which is vcc->user_back) and sets vcc->user_back to NULL. 2. In the second iteration, for the next matched ARP entry sharing the same VCC, lec_arp_clear_vccs() is called again. It obtains a NULL vpriv from vcc->user_back (via LEC_VCC_PRIV(vcc)) and then attempts to dereference it via `vcc->pop = vpriv->old_pop`, leading to a null-ptr-deref crash. Fix this by adding a null check for vpriv before dereferencing it. If vpriv is already NULL, it means the VCC has been cleared by a previous call, so we can safely skip the cleanup and just clear the entry's vcc/recv_vcc pointers. The entire cleanup block (including vcc_release_async()) is placed inside the vpriv guard because a NULL vpriv indicates the VCC has already been fully released by a prior iteration — repeating the teardown would redundantly set flags and trigger callbacks on an already-closing socket. The Fixes tag points to the initial commit because the entry->vcc path has been vulnerable since the original code. The entry->recv_vcc path was later added by commit 8d9f73c0ad2f ("atm: fix a memory leak of vcc->user_back") with the same pattern, and both paths are fixed here.
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Meta Information
Published
2026-03-25
Last Modified
2026-04-18
Generated
2026-05-07
AI Q&A
2026-03-25
EPSS Evaluated
2026-05-05
NVD
CVE-2026-23286
EUVD
EUVD-2026-15212
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a null pointer dereference in the Linux kernel's ATM LANE (LAN Emulation) module, specifically in the lec_arp_clear_vccs() function.

The issue occurs because multiple ARP entries can share the same atm_vcc (virtual circuit connection). When the underlying VCC is closed, the function lec_vcc_close() iterates over all ARP entries and calls lec_arp_clear_vccs() for each one.

During this iteration, the first call to lec_arp_clear_vccs() frees a resource (vpriv) and sets a pointer (vcc->user_back) to NULL. On the next iteration, lec_arp_clear_vccs() tries to dereference this now NULL pointer, causing a null pointer dereference crash.

The fix adds a null check before dereferencing the pointer to avoid the crash, skipping cleanup if the resource has already been released.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash due to a null pointer dereference, leading to a denial of service (DoS) condition.

If exploited or triggered, it could cause system instability or unexpected reboots, affecting availability of services running on the affected system.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability involves a null pointer dereference in the Linux kernel's ATM LANE module, specifically in the lec_arp_clear_vccs() function. It can be reproduced using the syzkaller reproducer tool.

To detect this vulnerability on your system, you can attempt to reproduce the issue using syzkaller, a kernel fuzzing tool designed to find such bugs.

There are no specific commands provided in the available information to detect this vulnerability directly on a running system or network.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability has been fixed by adding a null check in the lec_arp_clear_vccs() function to prevent dereferencing a NULL pointer.

Immediate mitigation steps include updating the Linux kernel to a version that contains this fix.

No other specific mitigation steps or workarounds are provided in the available information.


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