{"cve":"CVE-2026-23276","nvd":{"published":"2026-03-20T09:16:13.370","modified":"2026-10-21T13:18:35.440","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: add xmit recursion limit to tunnel xmit functions\n\nTunnel xmit functions (iptunnel_xmit, ip6tunnel_xmit) lack their own\nrecursion limit. When a bond device in broadcast mode has GRE tap\ninterfaces as slaves, and those GRE tunnels route back through the\nbond, multicast/broadcast traffic triggers infinite recursion between\nbond_xmit_broadcast() and ip_tunnel_xmit()/ip6_tnl_xmit(), causing\nkernel stack overflow.\n\nThe existing XMIT_RECURSION_LIMIT (8) in the no-qdisc path is not\nsufficient because tunnel recursion involves route lookups and full IP\noutput, consuming much more stack per level. Use a lower limit of 4\n(IP_TUNNEL_RECURSION_LIMIT) to prevent overflow.\n\nAdd recursion detection using dev_xmit_recursion helpers directly in\niptunnel_xmit() and ip6tunnel_xmit() to cover all IPv4/IPv6 tunnel\npaths including UDP encapsulated tunnels (VXLAN, Geneve, etc.).\n\nMove dev_xmit_recursion helpers from net/core/dev.h to public header\ninclude/linux/netdevice.h so they can be used by tunnel code.\n\n BUG: KASAN: stack-out-of-bounds in blake2s.constprop.0+0xe7/0x160\n Write of size 32 at addr ffff88810033fed0 by task kworker/0:1/11\n Workqueue: mld mld_ifc_work\n Call Trace:\n  <TASK>\n  __build_flow_key.constprop.0 (net/ipv4/route.c:515)\n  ip_rt_update_pmtu (net/ipv4/route.c:1073)\n  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:84)\n  ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847)\n  gre_tap_xmit (net/ipv4/ip_gre.c:779)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  sch_direct_xmit (net/sched/sch_generic.c:347)\n  __dev_queue_xmit (net/core/dev.c:4802)\n  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)\n  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)\n  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  __dev_queue_xmit (net/core/dev.c:4841)\n  ip_finish_output2 (net/ipv4/ip_output.c:237)\n  ip_output (net/ipv4/ip_output.c:438)\n  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86)\n  gre_tap_xmit (net/ipv4/ip_gre.c:779)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  sch_direct_xmit (net/sched/sch_generic.c:347)\n  __dev_queue_xmit (net/core/dev.c:4802)\n  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)\n  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)\n  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  __dev_queue_xmit (net/core/dev.c:4841)\n  ip_finish_output2 (net/ipv4/ip_output.c:237)\n  ip_output (net/ipv4/ip_output.c:438)\n  iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86)\n  ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847)\n  gre_tap_xmit (net/ipv4/ip_gre.c:779)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  sch_direct_xmit (net/sched/sch_generic.c:347)\n  __dev_queue_xmit (net/core/dev.c:4802)\n  bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312)\n  bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279)\n  bond_start_xmit (drivers/net/bonding/bond_main.c:5530)\n  dev_hard_start_xmit (net/core/dev.c:3887)\n  __dev_queue_xmit (net/core/dev.c:4841)\n  mld_sendpack\n  mld_ifc_work\n  process_one_work\n  worker_thread\n  </TASK>","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-674"],"references":["https://git.kernel.org/stable/c/6f1a9140ecda3baba3d945b9a6155af4268aafc4","https://git.kernel.org/stable/c/834c4f645726a25fd71ea50cdfb5c135f8f95d85","https://git.kernel.org/stable/c/8a57deeb256069f262957d8012418559ff66c385","https://git.kernel.org/stable/c/b56b8d19bd05e2a8338385c770bc2b60590bc81e","https://git.kernel.org/stable/c/da5f0166cef3d4285ddbb1b638661263fc03ee92"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2026-23276","score":0.00179,"percentile":0.07433,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}