GHSA-6RJ2-XG9P-3JJ4
Vulnerability from github – Published: 2026-03-25 12:30 – Updated: 2026-05-29 18:31In 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:
- 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.
- 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.
{
"affected": [],
"aliases": [
"CVE-2026-23286"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-25T11:16:23Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\natm: lec: fix null-ptr-deref in lec_arp_clear_vccs\n\nsyzkaller reported a null-ptr-deref in lec_arp_clear_vccs().\nThis issue can be easily reproduced using the syzkaller reproducer.\n\nIn the ATM LANE (LAN Emulation) module, the same atm_vcc can be shared by\nmultiple lec_arp_table entries (e.g., via entry-\u003evcc or entry-\u003erecv_vcc).\nWhen the underlying VCC is closed, lec_vcc_close() iterates over all\nARP entries and calls lec_arp_clear_vccs() for each matched entry.\n\nFor example, when lec_vcc_close() iterates through the hlists in\npriv-\u003elec_arp_empty_ones or other ARP tables:\n\n1. In the first iteration, for the first matched ARP entry sharing the VCC,\nlec_arp_clear_vccs() frees the associated vpriv (which is vcc-\u003euser_back)\nand sets vcc-\u003euser_back to NULL.\n2. In the second iteration, for the next matched ARP entry sharing the same\nVCC, lec_arp_clear_vccs() is called again. It obtains a NULL vpriv from\nvcc-\u003euser_back (via LEC_VCC_PRIV(vcc)) and then attempts to dereference it\nvia `vcc-\u003epop = vpriv-\u003eold_pop`, leading to a null-ptr-deref crash.\n\nFix this by adding a null check for vpriv before dereferencing\nit. If vpriv is already NULL, it means the VCC has been cleared\nby a previous call, so we can safely skip the cleanup and just\nclear the entry\u0027s vcc/recv_vcc pointers.\n\nThe entire cleanup block (including vcc_release_async()) is placed inside\nthe vpriv guard because a NULL vpriv indicates the VCC has already been\nfully released by a prior iteration \u2014 repeating the teardown would\nredundantly set flags and trigger callbacks on an already-closing socket.\n\nThe Fixes tag points to the initial commit because the entry-\u003evcc path has\nbeen vulnerable since the original code. The entry-\u003erecv_vcc path was later\nadded by commit 8d9f73c0ad2f (\"atm: fix a memory leak of vcc-\u003euser_back\")\nwith the same pattern, and both paths are fixed here.",
"id": "GHSA-6rj2-xg9p-3jj4",
"modified": "2026-05-29T18:31:13Z",
"published": "2026-03-25T12:30:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23286"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/101bacb303e89dc2e0640ae6a5e0fb97c4eb45bb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2d9f57ea29a1f1772373b98a509b44d49fda609e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/30c9744a989feb22cfbb84170eb0e038a7a2c1da"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5f1cfea7921f5c126a441d973690eeba52677b64"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/622062f24644b4536d3f437e0cf7a8c4bb421665"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7ea92ab075d809ec8a96669a5ecf00f752057875"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8aff65a82b6389ec674d46e5b3d3ae6f07db5e3e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e9665986eb127290ceb535bd5d04d7a84265d94f"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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