high · 7.5

sctp: disable BH before calling udp_tunnel_xmit_skb()

CVE-2026-53070 · published 24 Jun 2026

How serious is it

  • Severity: high, CVSS score 7.5 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-53070?

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Who is affected

  • Linux Linux: 046c052b475e7119b6a30e3483e2888fc606a2f8 to < 7f0062c40781fe0a340965f5bb0816681982ff4c, 046c052b475e7119b6a30e3483e2888fc606a2f8 to < be3bfcb34bda04f6a350710db471d4133f950f2c, 046c052b475e7119b6a30e3483e2888fc606a2f8 to < 0de7db2eb27e82b983157016fa604b1ba664ae5f, 046c052b475e7119b6a30e3483e2888fc606a2f8 to < 790093245e35040c2adb15f48970020425aa3f47
  • Linux Linux: 5.11

How to check

  1. Find out whether you run the affected product and which version, then compare it with the versions above.

How to fix

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  1. Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
  2. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

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

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References

Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON

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