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Unity Linux 20.1050e Security Update: kernel (UTSA-2026-006571)
medium Nessus Plugin ID 305354
Synopsis
The Unity Linux host is missing one or more security updates.Description
The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-006571 advisory.In the Linux kernel, the following vulnerability has been resolved:
tun: Fix memory leak for detached NAPI queue.
syzkaller reported [0] memory leaks of sk and skb related to the TUN device with no repro, but we can reproduce it easily with:
struct ifreq ifr = {} int fd_tun, fd_tmp;
char buf[4] = {};
fd_tun = openat(AT_FDCWD, /dev/net/tun, O_WRONLY, 0);
ifr.ifr_flags = IFF_TUN | IFF_NAPI | IFF_MULTI_QUEUE;
ioctl(fd_tun, TUNSETIFF, &ifr);
ifr.ifr_flags = IFF_DETACH_QUEUE;
ioctl(fd_tun, TUNSETQUEUE, &ifr);
fd_tmp = socket(AF_PACKET, SOCK_PACKET, 0);
ifr.ifr_flags = IFF_UP;
ioctl(fd_tmp, SIOCSIFFLAGS, &ifr);
write(fd_tun, buf, sizeof(buf));
close(fd_tun);
If we enable NAPI and multi-queue on a TUN device, we can put skb into tfile->sk.sk_write_queue after the queue is detached. We should prevent it by checking tfile->detached before queuing skb.
Note this must be done under tfile->sk.sk_write_queue.lock because write() and ioctl(IFF_DETACH_QUEUE) can run concurrently. Otherwise, there would be a small race window:
write() ioctl(IFF_DETACH_QUEUE) `- tun_get_user `- __tun_detach |- if (tfile->detached) |- tun_disable_queue | `-> false | `- tfile->detached = tun | `- tun_queue_purge |- spin_lock_bh(&queue->lock) `- __skb_queue_tail(queue, skb)
Another solution is to call tun_queue_purge() when closing and reattaching the detached queue, but it could paper over another problems. Also, we do the same kind of test for IFF_NAPI_FRAGS.
[0]:
unreferenced object 0xffff88801edbc800 (size 2048):
comm syz-executor.1, pid 33269, jiffies 4295743834 (age 18.756s) hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............
backtrace:
[<000000008c16ea3d>] __do_kmalloc_node mm/slab_common.c:965 [inline] [<000000008c16ea3d>] __kmalloc+0x4a/0x130 mm/slab_common.c:979 [<000000003addde56>] kmalloc include/linux/slab.h:563 [inline] [<000000003addde56>] sk_prot_alloc+0xef/0x1b0 net/core/sock.c:2035 [<000000003e20621f>] sk_alloc+0x36/0x2f0 net/core/sock.c:2088 [<0000000028e43843>] tun_chr_open+0x3d/0x190 drivers/net/tun.c:3438 [<000000001b0f1f28>] misc_open+0x1a6/0x1f0 drivers/char/misc.c:165 [<000000004376f706>] chrdev_open+0x111/0x300 fs/char_dev.c:414 [<00000000614d379f>] do_dentry_open+0x2f9/0x750 fs/open.c:920 [<000000008eb24774>] do_open fs/namei.c:3636 [inline] [<000000008eb24774>] path_openat+0x143f/0x1a30 fs/namei.c:3791 [<00000000955077b5>] do_filp_open+0xce/0x1c0 fs/namei.c:3818 [<00000000b78973b0>] do_sys_openat2+0xf0/0x260 fs/open.c:1356 [<00000000057be699>] do_sys_open fs/open.c:1372 [inline] [<00000000057be699>] __do_sys_openat fs/open.c:1388 [inline] [<00000000057be699>] __se_sys_openat fs/open.c:1383 [inline] [<00000000057be699>] __x64_sys_openat+0x83/0xf0 fs/open.c:1383 [<00000000a7d2182d>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<00000000a7d2182d>] do_syscall_64+0x3c/0x90 arch/x86/entry/common.c:80 [<000000004cc4e8c4>] entry_SYSCALL_64_after_hwframe+0x72/0xdc
unreferenced object 0xffff88802f671700 (size 240):
comm syz-executor.1, pid 33269, jiffies 4295743854 (age 18.736s) hex dump (first 32 bytes):
68 c9 db 1e 80 88 ff ff 68 c9 db 1e 80 88 ff ff h.......h.......
00 c0 7b 2f 80 88 ff ff 00 c8 db 1e 80 88 ff ff ..{/............
backtrace:
[<00000000e9d9fdb6>] __alloc_skb+0x223/0x250 net/core/skbuff.c:644 [<000000002c3e4e0b>] alloc_skb include/linux/skbuff.h:1288 [inline] [<000000002c3e4e0b>] alloc_skb_with_frags+0x6f/0x350 net/core/skbuff.c:6378 [<00000000825f98d7>] sock_alloc_send_pskb+0x3ac/0x3e0 net/core/sock.c:2729 [<00000000e9eb3df3>] tun_alloc_skb drivers/net/tun.c:1529 [inline] [<
---truncated---
Tenable has extracted the preceding description block directly from the Unity Linux security advisory.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
Solution
Update the affected kernel package.See Also
http://www.nessus.org/u?c276941e
Plugin Details
Severity: Medium
ID: 305354
File Name: unity_linux_UTSA-2026-006571.nasl
Version: 1.1
Type: Local
Published: 4/8/2026
Updated: 4/8/2026
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.4
CVSS v2
Risk Factor: Medium
Base Score: 4.6
Temporal Score: 3.4
Vector: CVSS2#AV:L/AC:L/Au:S/C:N/I:N/A:C
CVSS Score Source: CVE-2023-53685
CVSS v3
Risk Factor: Medium
Base Score: 5.5
Temporal Score: 4.8
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C
Vulnerability Information
Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list
Exploit Ease: No known exploits are available
Patch Publication Date: 4/8/2026
Vulnerability Publication Date: 6/27/2023
Reference Information
CVE: CVE-2023-53685