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CVE-2026-85035

Use-after-free via dynamically allocated message queue retained by the CAN RX filter

No exploitation reported by the sources we read.

  • Published2026-11-03
  • WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The can_add_rx_filter_msgq() system call installs a CAN RX filter whose callback (can_msgq_put() in drivers/can/can_common.c) is handed the caller's struct k_msgq * as user_data. The controller driver stores that raw pointer in its filter table and dereferences it from the RX path every time a matching frame arrives. The system call verifier z_vrfy_can_add_rx_filter_msgq() in drivers/can/can_handlers.c validated the queue only with K_SYSCALL_OBJ(), which is a point-in-time check of type, initialization and caller permission and says nothing about the object's lifetime. On a build with CONFIG_USERSPACE=y and CONFIG_DYNAMIC_OBJECTS=y, an unprivileged user-mode thread that has been granted access to a CAN device can obtain a message queue whose lifetime it fully controls: k_object_alloc(K_OBJ_MSGQ) followed by k_msgq_alloc_init(). The lifetime of such an object is driven solely by its permission bitmask, and a pointer retained by the kernel is not represented there. After registering the filter, the thread calls k_object_release() — or simply terminates — and unref_check() frees the struct k_msgq storage while the CAN driver still holds the pointer. The next matching CAN frame causes k_msgq_put() to run in supervisor context against freed memory that the attacker can have groomed with another kernel allocation: the frame payload is memcpy()d through the reused block's write_ptr, and the queue's wait_q (and poll_events under CONFIG_POLL) list nodes are manipulated. This yields kernel-heap corruption reachable from a user-mode thread, defeating the isolation CONFIG_USERSPACE is intended to provide; the same dangling pointer also arises benignly when an application thread exits without calling can_remove_rx_filter(). The fix validates the queue with K_SYSCALL_OBJ_STATIC(), which additionally rejects objects carrying K_OBJ_FLAG_ALLOC, so only statically defined queues (CAN_MSGQ_DEFINE()) may be registered from user mode. Supervisor-mode callers bypass the verifier and must themselves keep the queue valid until the filter is removed.

Timeline

dates in UTC
  1. 2026-11-0313:36CVE publishedCNA

Observed activity

isMalicious corpus · updated 2026-11-03 09:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-85035?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-85035?format=csv
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Versions per branch

Products declared by the CNA

As zephyr, the CNA that assigned this CVE, declared them in the CVE record; versions as written. NVD lists no product for this CVE yet: this is the only product data so far.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-03

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-85035 yet.

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVE recordread 2026-11-03
  • CNACVSS 3.18.82026-11-03
  • CNAweakness (CWE)CWE-4162026-11-03

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Published
2026-11-03
Last Modified
2026-11-03
NVD status
Awaiting Analysis

Frequently asked questions

What is CVE-2026-85035?

The can_add_rx_filter_msgq() system call installs a CAN RX filter whose callback (can_msgq_put() in drivers/can/can_common.c) is handed the caller's struct k_msgq * as user_data. The controller driver stores that raw pointer in its filter table and dereferences it from the RX path every time a matching frame arrives. The system call verifier z_vrfy_can_add_rx_filter_msgq() in drivers/can/can_handlers.c validated the queue only with K_SYSCALL_OBJ(), which is a point-in-time check of type, initialization and caller permission and says nothing about the object's lifetime. On a build with CONFIG_USERSPACE=y and CONFIG_DYNAMIC_OBJECTS=y, an unprivileged user-mode thread that has been granted access to a CAN device can obtain a message queue whose lifetime it fully controls: k_object_alloc(K_OBJ_MSGQ) followed by k_msgq_alloc_init(). The lifetime of such an object is driven solely by its permission bitmask, and a pointer retained by the kernel is not represented there. After registering the filter, the thread calls k_object_release() — or simply terminates — and unref_check() frees the struct k_msgq storage while the CAN driver still holds the pointer. The next matching CAN frame causes k_msgq_put() to run in supervisor context against freed memory that the attacker can have groomed with another kernel allocation: the frame payload is memcpy()d through the reused block's write_ptr, and the queue's wait_q (and poll_events under CONFIG_POLL) list nodes are manipulated. This yields kernel-heap corruption reachable from a user-mode thread, defeating the isolation CONFIG_USERSPACE is intended to provide; the same dangling pointer also arises benignly when an application thread exits without calling can_remove_rx_filter(). The fix validates the queue with K_SYSCALL_OBJ_STATIC(), which additionally rejects objects carrying K_OBJ_FLAG_ALLOC, so only statically defined queues (CAN_MSGQ_DEFINE()) may be registered from user mode. Supervisor-mode callers bypass the verifier and must themselves keep the queue valid until the filter is removed.

Is CVE-2026-85035 actively exploited?

Active exploitation of CVE-2026-85035 has not been confirmed.

What is the CVSS score for CVE-2026-85035?

CVE-2026-85035 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

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