CVE-2026-53070 (GCVE-0-2026-53070)
Vulnerability from cvelistv5
Published
2026-06-24 16:30
Modified
2026-10-21 12:41
Summary
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
Impacted products
Vendor Product Version
Linux Linux Version: 046c052b475e7119b6a30e3483e2888fc606a2f8
Version: 046c052b475e7119b6a30e3483e2888fc606a2f8
Version: 046c052b475e7119b6a30e3483e2888fc606a2f8
Version: 046c052b475e7119b6a30e3483e2888fc606a2f8
Version: 046c052b475e7119b6a30e3483e2888fc606a2f8
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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() -\u003e 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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This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.\\nC:N - The bug corrupts transmit recursion accounting, not packet contents or attacker-readable memory. I found no evidence of an information disclosure primitive.\\nI:N - The issue causes incorrect recursion detection and packet drops, not arbitrary writes, control-flow hijack, or attacker-controlled data modification. The only modified state is internal transmit recursion accounting.\\nA:H - Unbalanced per-CPU transmit recursion counters can become stale or underflowed, causing false recursion-limit detection and persistent packet drops in tunnel or device transmit paths. 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After commit 6f1a9140ecda (\\\"add xmit recursion limit to\\ntunnel xmit functions\\\"), on the path:\\n\\n  udp(6)_tunnel_xmit_skb() -\u003e 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. 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}


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  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
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