UBUNTU-CVE-2026-23095
In the Linux kernel, the following vulnerability has been resolved: gue: Fix skb memleak with inner IP protocol 0. syzbot reported skb memleak below. [0] The repro generated a GUE packet with its inner protocol 0. gue_udp_recv() returns -guehdr->proto_ctype for "resubmit" in ip_protocol_deliver_rcu(), but this only works with non-zero protocol number. Let's drop such packets. Note that 0 is a valid number (IPv6 Hop-by-Hop Option). I think it is not practical to encap HOPOPT in GUE, so once someone starts to complain, we could pass down a resubmit flag pointer to distinguish two zeros from the upper layer: * no error * resubmit HOPOPT [0] BUG: memory leak unreferenced object 0xffff888109695a00 (size 240): comm "syz.0.17", pid 6088, jiffies 4294943096 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00 .@.............. backtrace (crc a84b336f): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270 __build_skb+0x23/0x60 net/core/skbuff.c:474 build_skb+0x20/0x190 net/core/skbuff.c:490 __tun_build_skb drivers/net/tun.c:1541 [inline] tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636 tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770 tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x45d/0x710 fs/read_write.c:686 ksys_write+0xa7/0x170 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
53 explicit affected versions
116 explicit affected versions
82 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
19 explicit affected versions
10 explicit affected versions
6 explicit affected versions
92 explicit affected versions
24 explicit affected versions
77 explicit affected versions
77 explicit affected versions
91 explicit affected versions
80 explicit affected versions
72 explicit affected versions
10 explicit affected versions
34 explicit affected versions
26 explicit affected versions
84 explicit affected versions
7 explicit affected versions
79 explicit affected versions
38 explicit affected versions
13 explicit affected versions
85 explicit affected versions
41 explicit affected versions
35 explicit affected versions
44 explicit affected versions
42 explicit affected versions
18 explicit affected versions
36 explicit affected versions
118 explicit affected versions
64 explicit affected versions
43 explicit affected versions
120 explicit affected versions
13 explicit affected versions
4 explicit affected versions
121 explicit affected versions
23 explicit affected versions
49 explicit affected versions
124 explicit affected versions
1 explicit affected versions
1 explicit affected versions
21 explicit affected versions
9 explicit affected versions
16 explicit affected versions
10 explicit affected versions
20 explicit affected versions
76 explicit affected versions
45 explicit affected versions
8 explicit affected versions
7 explicit affected versions
12 explicit affected versions
11 explicit affected versions
111 explicit affected versions
7 explicit affected versions
12 explicit affected versions
14 explicit affected versions
10 explicit affected versions
1 explicit affected versions
7 explicit affected versions
13 explicit affected versions
104 explicit affected versions
12 explicit affected versions
8 explicit affected versions
105 explicit affected versions
12 explicit affected versions
38 explicit affected versions
120 explicit affected versions
38 explicit affected versions
16 explicit affected versions
17 explicit affected versions
25 explicit affected versions
31 explicit affected versions
10 explicit affected versions
37 explicit affected versions
10 explicit affected versions
9 explicit affected versions
13 explicit affected versions
37 explicit affected versions
3 explicit affected versions
10 explicit affected versions
11 explicit affected versions
59 explicit affected versions
1 explicit affected versions
26 explicit affected versions
8 explicit affected versions
13 explicit affected versions
144 explicit affected versions
32 explicit affected versions
1 explicit affected versions
29 explicit affected versions
111 explicit affected versions
13 explicit affected versions
12 explicit affected versions
89 explicit affected versions
38 explicit affected versions
38 explicit affected versions
8 explicit affected versions
1 explicit affected versions
100 explicit affected versions
84 explicit affected versions
47 explicit affected versions
33 explicit affected versions
23 explicit affected versions
53 explicit affected versions
10 explicit affected versions
17 explicit affected versions
188 explicit affected versions
16 explicit affected versions
11 explicit affected versions
5 explicit affected versions
12 explicit affected versions
9 explicit affected versions
7 explicit affected versions
12 explicit affected versions
8 explicit affected versions
16 explicit affected versions
138 explicit affected versions
2 explicit affected versions
5 explicit affected versions
69 explicit affected versions
132 explicit affected versions
85 explicit affected versions
165 explicit affected versions
154 explicit affected versions
10 explicit affected versions
26 explicit affected versions
35 explicit affected versions
1 explicit affected versions
61 explicit affected versions
33 explicit affected versions
44 explicit affected versions
11 explicit affected versions
10 explicit affected versions
13 explicit affected versions
43 explicit affected versions
139 explicit affected versions
78 explicit affected versions
16 explicit affected versions
83 explicit affected versions
47 explicit affected versions
116 explicit affected versions
3 explicit affected versions
132 explicit affected versions
93 explicit affected versions
1 explicit affected versions
7 explicit affected versions
2 explicit affected versions
15 explicit affected versions
51 explicit affected versions
16 explicit affected versions
92 explicit affected versions
18 explicit affected versions
39 explicit affected versions
12 explicit affected versions
66 explicit affected versions
72 explicit affected versions
7 explicit affected versions
27 explicit affected versions
58 explicit affected versions
121 explicit affected versions
1 explicit affected versions
1 explicit affected versions
98 explicit affected versions
40 explicit affected versions
8 explicit affected versions
49 explicit affected versions
5 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
7 explicit affected versions
43 explicit affected versions
13 explicit affected versions
110 explicit affected versions
13 explicit affected versions
72 explicit affected versions
7 explicit affected versions
140 explicit affected versions
8 explicit affected versions
94 explicit affected versions
10 explicit affected versions
12 explicit affected versions
9 explicit affected versions
31 explicit affected versions
108 explicit affected versions
80 explicit affected versions
56 explicit affected versions
44 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
48 explicit affected versions
14 explicit affected versions
38 explicit affected versions
167 explicit affected versions
9 explicit affected versions
17 explicit affected versions
11 explicit affected versions
36 explicit affected versions
17 explicit affected versions
14 explicit affected versions
85 explicit affected versions
8 explicit affected versions
7 explicit affected versions
97 explicit affected versions
121 explicit affected versions
4 explicit affected versions
74 explicit affected versions
8 explicit affected versions
1 explicit affected versions
1 explicit affected versions
1 explicit affected versions
83 explicit affected versions
73 explicit affected versions
73 explicit affected versions
13 explicit affected versions
43 explicit affected versions
77 explicit affected versions
14 explicit affected versions
119 explicit affected versions
10 explicit affected versions
8 explicit affected versions
42 explicit affected versions
88 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
14 explicit affected versions
11 explicit affected versions
1 explicit affected versions
69 explicit affected versions
123 explicit affected versions
16 explicit affected versions
37 explicit affected versions
73 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: gue: Fix skb memleak with inner IP protocol 0. syzbot reported skb memleak below. [0] The repro generated a GUE packet with its inner protocol 0. gue_udp_recv() returns -guehdr->proto_ctype for "resubmit" in ip_protocol_deliver_rcu(), but this only works with non-zero protocol number. Let's drop such packets. Note that 0 is a valid number (IPv6 Hop-by-Hop Option). I think it is not practical to encap HOPOPT in GUE, so once someone starts to complain, we could pass down a resubmit flag pointer to distinguish two zeros from the upper layer: * no error * resubmit HOPOPT [0] BUG: memory leak unreferenced object 0xffff888109695a00 (size 240): comm "syz.0.17", pid 6088, jiffies 4294943096 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00 .@.............. backtrace (crc a84b336f): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270 __build_skb+0x23/0x60 net/core/skbuff.c:474 build_skb+0x20/0x190 net/core/skbuff.c:490 __tun_build_skb drivers/net/tun.c:1541 [inline] tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636 tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770 tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x45d/0x710 fs/read_write.c:686 ksys_write+0xa7/0x170 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/9a56796ad258786d3624eef5aefba394fc9bdded
- https://git.kernel.org/stable/c/5437a279804ced8088cabb945dba88a26d828f8c
- https://git.kernel.org/stable/c/9a56796ad258786d3624eef5aefba394fc9bdded
- https://git.kernel.org/stable/c/ce569b389a5c78d64788a5ea94560e17fa574b35
- https://git.kernel.org/stable/c/f87b9b7a618c82e7465e872eb10e14c803871892
- https://ubuntu.com/security/CVE-2026-23095
- https://ubuntu.com/security/notices/USN-8162-1
- https://ubuntu.com/security/notices/USN-8180-1
- https://ubuntu.com/security/notices/USN-8180-2
- https://ubuntu.com/security/notices/USN-8180-3
- https://ubuntu.com/security/notices/USN-8180-4
- https://ubuntu.com/security/notices/USN-8180-5
- https://ubuntu.com/security/notices/USN-8180-6
- https://ubuntu.com/security/notices/USN-8186-1
- https://ubuntu.com/security/notices/USN-8187-1
- https://ubuntu.com/security/notices/USN-8188-1
- https://ubuntu.com/security/notices/USN-8243-1
- https://ubuntu.com/security/notices/USN-8275-1
- https://ubuntu.com/security/notices/USN-8278-1
- https://ubuntu.com/security/notices/USN-8278-2
- https://ubuntu.com/security/notices/USN-8289-1
- https://ubuntu.com/security/notices/USN-8289-2
- https://ubuntu.com/security/notices/USN-8296-1
- https://ubuntu.com/security/notices/USN-8296-2
- https://ubuntu.com/security/notices/USN-8297-1
- https://ubuntu.com/security/notices/USN-8393-1
- https://ubuntu.com/security/notices/USN-8440-1
- https://ubuntu.com/security/notices/USN-8499-1
- https://ubuntu.com/security/notices/USN-8570-1
- https://ubuntu.com/security/notices/USN-8570-2
- https://ubuntu.com/security/notices/USN-8594-1
- https://ubuntu.com/security/notices/USN-8604-1
- https://ubuntu.com/security/notices/USN-8605-1
- https://www.cve.org/CVERecord?id=CVE-2026-23095