CVE-2026-53070

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

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0035

Probability of exploitation

0.27%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other References

https://git.kernel.org/stable/c/0de7db2eb27e82b983157016fa604b1ba664ae5f https://git.kernel.org/stable/c/2cd7e6971fc2787408ceef17906ea152791448cf https://git.kernel.org/stable/c/790093245e35040c2adb15f48970020425aa3f47

Frequently Asked Questions

What is CVE-2026-53070? +

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 It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-53070? +

CVE-2026-53070 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0035, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-53070? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.