From d3915a1f5a4bc0ac911032903c3c6ab8df9fcc7c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 2 Jun 2026 16:15:47 +0000 Subject: [PATCH] ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options This patch restricts setting Loose Source and Record Route (LSRR) and Strict Source and Record Route (SSRR) IP options to users with CAP_NET_RAW capability. This prevents unprivileged applications from forcing packets to route through attacker-controlled nodes to leak TCP ISN and possibly other protocol information. While LSRR and SSRR are commonly filtered in many network environments, they may still be supported and forwarded along some network paths. RFC 7126 (Recommendations on Filtering of IPv4 Packets Containing IPv4 Options) recommend to drop these options in 4.3 and 4.4. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Tamir Shahar Reported-by: Amit Klein Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260602161547.2642155-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv4/ip_options.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c index be8815ce3ac2..09d745112c15 100644 --- a/net/ipv4/ip_options.c +++ b/net/ipv4/ip_options.c @@ -530,6 +530,10 @@ int ip_options_get(struct net *net, struct ip_options_rcu **optp, kfree(opt); return -EINVAL; } + if (opt->opt.srr && !ns_capable(net->user_ns, CAP_NET_RAW)) { + kfree(opt); + return -EPERM; + } kfree(*optp); *optp = opt; return 0;