{"id":"CVE-2026-53070","state":"PUBLISHED","title":"sctp: disable BH before calling udp_tunnel_xmit_skb()","description":"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","publishedAt":"2026-06-24T16:30:11.816Z","updatedAt":"2026-10-30T12:26:35.465Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"e2933f5b3a31b175628985b92895269b778674a1","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"7f0062c40781fe0a340965f5bb0816681982ff4c","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"be3bfcb34bda04f6a350710db471d4133f950f2c","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"0de7db2eb27e82b983157016fa604b1ba664ae5f","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"790093245e35040c2adb15f48970020425aa3f47","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"2cd7e6971fc2787408ceef17906ea152791448cf","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sctp/ipv6.c","net/sctp/protocol.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.11","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.37","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.10","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sctp/ipv6.c","net/sctp/protocol.c"]}],"references":["https://git.kernel.org/stable/c/e2933f5b3a31b175628985b92895269b778674a1","https://git.kernel.org/stable/c/7f0062c40781fe0a340965f5bb0816681982ff4c","https://git.kernel.org/stable/c/be3bfcb34bda04f6a350710db471d4133f950f2c","https://git.kernel.org/stable/c/0de7db2eb27e82b983157016fa604b1ba664ae5f","https://git.kernel.org/stable/c/790093245e35040c2adb15f48970020425aa3f47","https://git.kernel.org/stable/c/2cd7e6971fc2787408ceef17906ea152791448cf"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-30T12:44:04.813Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53070.json","commit":"db8103c5921aac81d5d90efcf3745980dafabf49","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53070","state":"PUBLISHED","datePublished":"2026-06-24T16:30:11.816Z","dateUpdated":"2026-10-30T12:26:35.465Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-06-09T07:44:35.382Z"},"containers":{"cna":{"title":"sctp: disable BH before calling udp_tunnel_xmit_skb()","descriptions":[{"lang":"en","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"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"e2933f5b3a31b175628985b92895269b778674a1","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"7f0062c40781fe0a340965f5bb0816681982ff4c","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"be3bfcb34bda04f6a350710db471d4133f950f2c","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"0de7db2eb27e82b983157016fa604b1ba664ae5f","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"790093245e35040c2adb15f48970020425aa3f47","versionType":"git"},{"version":"046c052b475e7119b6a30e3483e2888fc606a2f8","status":"affected","lessThan":"2cd7e6971fc2787408ceef17906ea152791448cf","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sctp/ipv6.c","net/sctp/protocol.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.11","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.37","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.10","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sctp/ipv6.c","net/sctp/protocol.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e2933f5b3a31b175628985b92895269b778674a1"},{"url":"https://git.kernel.org/stable/c/7f0062c40781fe0a340965f5bb0816681982ff4c"},{"url":"https://git.kernel.org/stable/c/be3bfcb34bda04f6a350710db471d4133f950f2c"},{"url":"https://git.kernel.org/stable/c/0de7db2eb27e82b983157016fa604b1ba664ae5f"},{"url":"https://git.kernel.org/stable/c/790093245e35040c2adb15f48970020425aa3f47"},{"url":"https://git.kernel.org/stable/c/2cd7e6971fc2787408ceef17906ea152791448cf"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - SCTP-over-UDP transmit is reachable from network-facing SCTP endpoints when received packets or application-level requests cause replies through the SCTP output path. A remote peer can trigger the affected UDP-encapsulated transmit path in a reasonable SCTP service deployment.\nAC:L - The bug is triggered by repeatedly causing SCTP-over-UDP transmission in process/backlog context where BH is not disabled. Although CPU migration/preemption timing is involved, the attacker can drive repeated transmissions and the higher-severity choice is AC:L.\nPR:N - A remote SCTP peer does not need local credentials or kernel privileges to send packets to an SCTP-over-UDP service and induce responses. Local setup of SCTP-over-UDP may require configuration, but exploitation of an exposed configured service is unauthenticated.\nUI:N - No victim user action is required once an SCTP-over-UDP endpoint is exposed. The attacker only sends network traffic.\nS:U - The impact remains within the kernel networking stack and host network availability. 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. Repeated triggering can deny network availability for affected SCTP-over-UDP traffic and potentially broader transmit paths on affected CPUs."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:26:35.465Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.18.37"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"7.0.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-53070","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:25:08.024827Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:47:14.996Z"}}]}}}