git: 0692341b263e - releng/12.4 - pf: handle multiple IPv6 fragment headers

From: Gordon Tetlow <>
Date: Wed, 06 Sep 2023 17:37:44 UTC
The branch releng/12.4 has been updated by gordon:


commit 0692341b263e1baa17f5bbbe1d957b7e94eb647b
Author:     Kristof Provost <>
AuthorDate: 2023-07-28 09:39:33 +0000
Commit:     Gordon Tetlow <>
CommitDate: 2023-09-06 17:19:11 +0000

    pf: handle multiple IPv6 fragment headers
    With 'scrub fragment reassemble' if a packet contains multiple IPv6
    fragment headers we would reassemble the packet and immediately
    continue processing it.
    That is, we'd remove the first fragment header and expect the next
    header to be a final header (i.e. TCP, UDP, ICMPv6, ...). However, if
    it's another fragment header we'd not treat the packet correctly.
    That is, we'd fail to recognise the payload and treat it as if it were
    an IPv6 fragment rather than as its actual payload.
    Fix this by restarting the normalisation on the reassembled packet.
    If there are multiple fragment headers drop the packet.
    Reported by:    Enrico Bassetti (NetSecurityLab @ Sapienza University of Rome)
    Approved by:    so
    Security:       CVE-2023-4809
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    (cherry picked from commit 76afcbb52492f9b3e72ee7d4c4ed0a54c25e1c48)
    (cherry picked from commit 8922b9ac0b48749be42689ea959e6a1664f96b12)
 sys/netpfil/pf/pf_norm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/netpfil/pf/pf_norm.c b/sys/netpfil/pf/pf_norm.c
index ec063f82c1d9..9e936bcd1da5 100644
--- a/sys/netpfil/pf/pf_norm.c
+++ b/sys/netpfil/pf/pf_norm.c
@@ -1213,6 +1213,8 @@ pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kkif *kif,
 	if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len)
 		goto drop;
+	h = mtod(m, struct ip6_hdr *);
 	extoff = 0;
 	off = sizeof(struct ip6_hdr);
 	proto = h->ip6_nxt;
@@ -1303,6 +1305,8 @@ pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kkif *kif,
 	return (PF_PASS);
+	if (pd->flags & PFDESC_IP_REAS)
+		return (PF_DROP);
 	/* Jumbo payload packets cannot be fragmented. */
 	plen = ntohs(h->ip6_plen);
 	if (plen == 0 || jumbolen)
@@ -1324,7 +1328,7 @@ pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kkif *kif,
 		return (PF_DROP);
 	pd->flags |= PFDESC_IP_REAS;
-	return (PF_PASS);
+	goto again;