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
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
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
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Fixes
Solution
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Workaround
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References
History
Wed, 24 Jun 2026 17:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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 | |
| Title | sctp: disable BH before calling udp_tunnel_xmit_skb() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-06-24T16:30:11.816Z
Reserved: 2026-06-09T07:44:35.382Z
Link: CVE-2026-53070
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
Updated: 2026-06-24T19:30:08Z
Weaknesses
No weakness.