CVE: CVE-2023-53439
Published: 2025-09-18
Description: In the Linux kernel, the following vulnerability has been resolved:

net: skb_partial_csum_set() fix against transport header magic value

skb->transport_header uses the special 0xFFFF value
to mark if the transport header was set or not.

We must prevent callers to accidentaly set skb->transport_header
to 0xFFFF. Note that only fuzzers can possibly do this today.

syzbot reported:

WARNING: CPU: 0 PID: 2340 at include/linux/skbuff.h:2847 skb_transport_offset include/linux/skbuff.h:2956 [inline]
WARNING: CPU: 0 PID: 2340 at include/linux/skbuff.h:2847 virtio_net_hdr_to_skb+0xbcc/0x10c0 include/linux/virtio_net.h:103
Modules linked in:
CPU: 0 PID: 2340 Comm: syz-executor.0 Not tainted 6.3.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
RIP: 0010:skb_transport_header include/linux/skbuff.h:2847 [inline]
RIP: 0010:skb_transport_offset include/linux/skbuff.h:2956 [inline]
RIP: 0010:virtio_net_hdr_to_skb+0xbcc/0x10c0 include/linux/virtio_net.h:103
Code: 41 39 df 0f 82 c3 04 00 00 48 8b 7c 24 10 44 89 e6 e8 08 6e 59 ff 48 85 c0 74 54 e8 ce 36 7e fc e9 37 f8 ff ff e8 c4 36 7e fc <0f> 0b e9 93 f8 ff ff 44 89 f7 44 89 e6 e8 32 38 7e fc 45 39 e6 0f
RSP: 0018:ffffc[PII_REDACTED]0 EFLAGS: 00010293
RAX: ffffffff84fea55c RBX:[PII_REDACTED]00ffff RCX: ffff888120be2100
RDX: [PII_REDACTED] RSI:[PII_REDACTED]00ffff RDI:[PII_REDACTED]00ffff
RBP: ffffc[PII_REDACTED]0 R08: ffffffff84fe9de5 R09: [PII_REDACTED]
R10: ffffea00048ebd80 R11: [PII_REDACTED] R12: ffff88811dc2d9c8
R13: dffffc[PII_REDACTED] R14: ffff88811dc2d9ae R15: 1ffff11023b85b35
FS: 00007f9211a59700(0000) GS:ffff8881f6c00000(0000) knlGS:[PII_REDACTED]
CS: 0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2:[PII_REDACTED]0002c0 CR3:[PII_REDACTED]5a5000 CR4:[PII_REDACTED]3506f0
DR0: [PII_REDACTED] DR1: [PII_REDACTED] DR2: [PII_REDACTED]
DR3: [PII_REDACTED] DR6: 00000000fffe0ff0 DR7: [PII_REDACTED]
Call Trace:
<TASK>
packet_snd net/packet/af_packet.c:3076 [inline]
packet_sendmsg+0x4590/0x61a0 net/packet/af_packet.c:3115
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
__sys_sendto+0x472/0x630 net/socket.c:2144
__do_sys_sendto net/socket.c:2156 [inline]
__se_sys_sendto net/socket.c:2152 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2152
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2f/0x50 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9210c8c169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9211a59168 EFLAGS: 00000246 ORIG_RAX:[PII_REDACTED]00002c
RAX: ffffffffffffffda RBX: 00007f9210dabf80 RCX: 00007f9210c8c169
RDX:[PII_REDACTED]00ffed RSI:[PII_REDACTED]0000c0 RDI: [PII_REDACTED]
RBP: 00007f9210ce7ca1 R08: [PII_REDACTED] R09: [PII_REDACTED]
R10: [PII_REDACTED] R11: [PII_REDACTED] R12: [PII_REDACTED]
R13: 00007ffe135d65cf R14: 00007f9211a59300 R15: [PII_REDACTED]
CVSS Score: 5.5 (MEDIUM)
CWE: CWE-401, CWE-401
References: https://git.kernel.org/stable/c/3e785c8deb046305c61b9fa02265d0cb900c4a45; https://git.kernel.org/stable/c/424f8416bb39936df6365442d651ee729b283460; https://git.kernel.org/stable/c/70a76d[PII_REDACTED]d0464f71aafa126c84826628