In the Linux kernel, the following vulnerability has been resolved: net: serialize netif_running() check in enqueue_to_backlog() Syzbot reported a KASAN slab-use-after-free in fib_rules_lookup(). The root cause is a race condition where packets can escape the backlog flushing during device unregistration (e.g., during netns exit). Commit e9e4dd3267d0 ("net: do not process device backlog during unregistration") introduced a lockless netif_running() check in enqueue_to_backlog() to prevent queuing packets to an unregistering device. However, this creates a TOCTOU race window. A lockless transmitter (like veth_xmit) can pass the check before dev_close() clears IFF_UP. If the transmitter is then delayed, flush_all_backlogs() can run and finish before the transmitter grabs the backlog lock and queues the packet. The packet then escapes the flush and triggers UAF later when processed. Fix this by moving the netif_running() check inside the backlog lock. This serializes the check with the flush work (which also grabs the lock). We then either queue the packet before the flush runs (so it gets flushed), or check netif_running() after the flush/close completes (so it gets dropped).

The remote Ubuntu 24.04 LTS / 26.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-8816-1 advisory.

    Several security issues were discovered in the Linux kernel. An attacker could possibly use these to     compromise the system. This update corrects flaws in the following subsystems:

    - ARM64 architecture;

    - S390 architecture;

    - x86 architecture;

    - DRBD Distributed Replicated Block Device drivers;

    - InfiniBand drivers;

    - IOMMU subsystem;

    - Multiple devices driver;

    - Network drivers;

    - Microsoft Azure Network Adapter (MANA) driver;

    - NVME drivers;

    - TCM subsystem;

    - Virtio Host (VHOST) subsystem;

    - Xen hypervisor drivers;

    - AFS file system;

    - File systems infrastructure;

    - Network file systems library;

    - Network file system (NFS) client;

    - NTFS3 file system;

    - OCFS2 file system;

    - OrangeFS file system;

    - SMB network file system;

    - IPv4 networking;

    - Sun RPC protocol;

    - IPv6 networking;

    - IP tunnels definitions;

    - Netfilter;

    - TCP network protocol;

    - Locking primitives;

    - 9P file system network protocol;

    - B.A.T.M.A.N. meshing protocol;

    - Networking core;

    - IFE protocol;

    - RxRPC session sockets;

    - Network traffic control;

    - SCTP protocol;

    - SMC sockets;

    - TIPC protocol;

    - XFRM subsystem; (CVE-2026-64530, CVE-2026-64534, CVE-2026-64535, CVE-2026-64541, CVE-2026-64551,     CVE-2026-68083, CVE-2026-68457, CVE-2026-68476, CVE-2026-68477, CVE-2026-72014, CVE-2026-72020,     CVE-2026-72033, CVE-2026-72041, CVE-2026-72046, CVE-2026-72064, CVE-2026-72065, CVE-2026-72069,     CVE-2026-72083, CVE-2026-72084, CVE-2026-72085, CVE-2026-72098, CVE-2026-72129, CVE-2026-72130,     CVE-2026-72137, CVE-2026-72139, CVE-2026-72191, CVE-2026-72192, CVE-2026-72194, CVE-2026-72217,     CVE-2026-72220, CVE-2026-72221, CVE-2026-72222, CVE-2026-72226, CVE-2026-72234, CVE-2026-72248,     CVE-2026-72249, CVE-2026-72251, CVE-2026-72277, CVE-2026-72278, CVE-2026-72279, CVE-2026-72287,     CVE-2026-72288, CVE-2026-72289, CVE-2026-72296, CVE-2026-72299, CVE-2026-72317, CVE-2026-72318,     CVE-2026-72319, CVE-2026-72320, CVE-2026-72322, CVE-2026-72323, CVE-2026-72329, CVE-2026-72339,     CVE-2026-72348, CVE-2026-72351, CVE-2026-72355, CVE-2026-72366, CVE-2026-72381, CVE-2026-72393,     CVE-2026-72398, CVE-2026-72399, CVE-2026-72412, CVE-2026-72417, CVE-2026-72422, CVE-2026-72429,     CVE-2026-72436, CVE-2026-72442, CVE-2026-72451, CVE-2026-72463, CVE-2026-72466, CVE-2026-72472,     CVE-2026-72473, CVE-2026-72477, CVE-2026-72491, CVE-2026-72493, CVE-2026-72494, CVE-2026-72495,     CVE-2026-72496, CVE-2026-72501, CVE-2026-74255, CVE-2026-74267, CVE-2026-74268, CVE-2026-74269,     CVE-2026-74287, CVE-2026-74310, CVE-2026-74345, CVE-2026-74350, CVE-2026-74361, CVE-2026-74376,     CVE-2026-74384, CVE-2026-74394, CVE-2026-74398, CVE-2026-74401, CVE-2026-74406, CVE-2026-74427,     CVE-2026-74428, CVE-2026-74433, CVE-2026-74434, CVE-2026-74436, CVE-2026-74439, CVE-2026-80665)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - net: serialize netif_running() check in enqueue_to_backlog() Syzbot reported a KASAN slab-use-after-free     in fib_rules_lookup(). The root cause is a race condition where packets can escape the backlog flushing     during device unregistration (e.g., during netns exit). Commit e9e4dd3267d0 (net: do not process device     backlog during unregistration) introduced a lockless netif_running() check in enqueue_to_backlog() to     prevent queuing packets to an unregistering device. However, this creates a TOCTOU race window. A lockless     transmitter (like veth_xmit) can pass the check before dev_close() clears IFF_UP. If the transmitter is     then delayed, flush_all_backlogs() can run and finish before the transmitter grabs the backlog lock and     queues the packet. The packet then escapes the flush and triggers UAF later when processed. Fix this by     moving the netif_running() check inside the backlog lock. This serializes the check with the flush work     (which also grabs the lock). We then either queue the packet before the flush runs (so it gets flushed),     or check netif_running() after the flush/close completes (so it gets dropped). (CVE-2026-72493)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
365768	Ubuntu 26.04 LTS : Linux kernel (Azure) vulnerabilities (USN-8888-1)	Nessus	Ubuntu Local Security Checks	Local	medium
365283	Amazon Linux 2023 : bpftool6.18, kernel6.18, kernel6.18-devel (ALAS2023-2026-3187)	Nessus	Amazon Linux Local Security Checks	Local	medium
365279	Amazon Linux 2023 : bpftool6.12, kernel6.12, kernel6.12-devel (ALAS2023-2026-3196)	Nessus	Amazon Linux Local Security Checks	Local	medium
350177	Ubuntu 24.04 LTS / 26.04 LTS : Linux kernel vulnerabilities (USN-8816-1)	Nessus	Ubuntu Local Security Checks	Local	critical
335575	Linux Distros Unpatched Vulnerability : CVE-2026-72493	Nessus	Misc.	Local	critical

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