GHSA-FG3V-8P2H-99JG
Vulnerability from github – Published: 2026-02-04 18:30 – Updated: 2026-07-14 15:31In 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
{
"affected": [],
"aliases": [
"CVE-2026-23095"
],
"database_specific": {
"cwe_ids": [
"CWE-401"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-02-04T17:16:20Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ngue: Fix skb memleak with inner IP protocol 0.\n\nsyzbot reported skb memleak below. [0]\n\nThe repro generated a GUE packet with its inner protocol 0.\n\ngue_udp_recv() returns -guehdr-\u003eproto_ctype for \"resubmit\"\nin ip_protocol_deliver_rcu(), but this only works with\nnon-zero protocol number.\n\nLet\u0027s drop such packets.\n\nNote that 0 is a valid number (IPv6 Hop-by-Hop Option).\n\nI think it is not practical to encap HOPOPT in GUE, so once\nsomeone starts to complain, we could pass down a resubmit\nflag pointer to distinguish two zeros from the upper layer:\n\n * no error\n * resubmit HOPOPT\n\n[0]\nBUG: memory leak\nunreferenced object 0xffff888109695a00 (size 240):\n comm \"syz.0.17\", pid 6088, jiffies 4294943096\n hex dump (first 32 bytes):\n 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................\n 00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00 .@..............\n backtrace (crc a84b336f):\n kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]\n slab_post_alloc_hook mm/slub.c:4958 [inline]\n slab_alloc_node mm/slub.c:5263 [inline]\n kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270\n __build_skb+0x23/0x60 net/core/skbuff.c:474\n build_skb+0x20/0x190 net/core/skbuff.c:490\n __tun_build_skb drivers/net/tun.c:1541 [inline]\n tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636\n tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770\n tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999\n new_sync_write fs/read_write.c:593 [inline]\n vfs_write+0x45d/0x710 fs/read_write.c:686\n ksys_write+0xa7/0x170 fs/read_write.c:738\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f",
"id": "GHSA-fg3v-8p2h-99jg",
"modified": "2026-07-14T15:31:39Z",
"published": "2026-02-04T18:30:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23095"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/380a82d36e37db49fd41ecc378c22fd29392e96a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/536f5bbc322eb1e175bdd1ced22b236a951c4d8f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5437a279804ced8088cabb945dba88a26d828f8c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/886f186328b718400dbf79e1bc8cbcbd710ab766"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9a56796ad258786d3624eef5aefba394fc9bdded"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ce569b389a5c78d64788a5ea94560e17fa574b35"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f87b9b7a618c82e7465e872eb10e14c803871892"
}
],
"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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