CVE-2026-53070
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: sctp: disable BH before calling udp_tunnel_xmit_skb() udp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with BH disabled. After commit 6f1a9140ecda ("add xmit recursion limit to tunnel xmit functions"), on the path: udp(6)_tunnel_xmit_skb() -> ip(6)tunnel_xmit() dev_xmit_recursion_inc()/dec() must stay balanced on the same CPU. Without local_bh_disable(), the context may move between CPUs, which can break the inc/dec pairing. This may lead to incorrect recursion level detection and cause packets to be dropped in ip(6)_tunnel_xmit() or __dev_queue_xmit(). Fix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths. In my testing, after enabling the SCTP over UDP: # ip net exec ha sysctl -w net.sctp.udp_port=9899 # ip net exec ha sysctl -w net.sctp.encap_port=9899 # ip net exec hb sysctl -w net.sctp.udp_port=9899 # ip net exec hb sysctl -w net.sctp.encap_port=9899 # ip net exec ha iperf3 -s - without this patch: # ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 37.2 MBytes 31.2 Mbits/sec sender [ 5] 0.00-10.00 sec 37.1 MBytes 31.1 Mbits/sec receiver - with this patch: # ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec sender [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec receiver
Severity
HIGH
CVSS score
7.5
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-06-24 17:17:20.513000
Last modified
2026-10-30 13:19:09.543000
View original CVE JSON
{
"id": "CVE-2026-53070",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-06-24T17:17:20.513",
"lastModified": "2026-10-30T13:19:09.543",
"vulnStatus": "Modified",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: disable BH before calling udp_tunnel_xmit_skb()\n\nudp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with\nBH disabled. After commit 6f1a9140ecda (\"add xmit recursion limit to\ntunnel xmit functions\"), on the path:\n\n udp(6)_tunnel_xmit_skb() -> ip(6)tunnel_xmit()\n\ndev_xmit_recursion_inc()/dec() must stay balanced on the same CPU.\n\nWithout local_bh_disable(), the context may move between CPUs, which can\nbreak the inc/dec pairing. This may lead to incorrect recursion level\ndetection and cause packets to be dropped in ip(6)_tunnel_xmit() or\n__dev_queue_xmit().\n\nFix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths.\n\nIn my testing, after enabling the SCTP over UDP:\n\n # ip net exec ha sysctl -w net.sctp.udp_port=9899\n # ip net exec ha sysctl -w net.sctp.encap_port=9899\n # ip net exec hb sysctl -w net.sctp.udp_port=9899\n # ip net exec hb sysctl -w net.sctp.encap_port=9899\n\n # ip net exec ha iperf3 -s\n\n- without this patch:\n\n # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n [ 5] 0.00-10.00 sec 37.2 MBytes 31.2 Mbits/sec sender\n [ 5] 0.00-10.00 sec 37.1 MBytes 31.1 Mbits/sec receiver\n\n- with this patch:\n\n # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec sender\n [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec receiver"
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