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CVE-2026-23276— net: add xmit recursion limit to tunnel xmit functions

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于隧道发送函数缺少发送递归限制，可能导致无限递归和内核堆栈溢出。

AI Predicted 5.3 Difficulty: Moderate EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux 745e20f1b626b1be4b100af5d4bf7b3439392f8f< 834c4f645726a25fd71ea50cdfb5c135f8f95d85 affected
745e20f1b626b1be4b100af5d4bf7b3439392f8f< 8a57deeb256069f262957d8012418559ff66c385 affected
745e20f1b626b1be4b100af5d4bf7b3439392f8f< b56b8d19bd05e2a8338385c770bc2b60590bc81e affected
745e20f1b626b1be4b100af5d4bf7b3439392f8f< 6f1a9140ecda3baba3d945b9a6155af4268aafc4 affected
3f266b04185de51d8e6446eb1fccec3b5e7ce575 affected
2.6.35.9< 2.6.36 affected
2.6.37 affected
< 2.6.37 unaffected
… +4 more rows
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I. Basic Information for CVE-2026-23276

Vulnerability Information
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Vulnerability Title
net: add xmit recursion limit to tunnel xmit functions
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: add xmit recursion limit to tunnel xmit functions Tunnel xmit functions (iptunnel_xmit, ip6tunnel_xmit) lack their own recursion limit. When a bond device in broadcast mode has GRE tap interfaces as slaves, and those GRE tunnels route back through the bond, multicast/broadcast traffic triggers infinite recursion between bond_xmit_broadcast() and ip_tunnel_xmit()/ip6_tnl_xmit(), causing kernel stack overflow. The existing XMIT_RECURSION_LIMIT (8) in the no-qdisc path is not sufficient because tunnel recursion involves route lookups and full IP output, consuming much more stack per level. Use a lower limit of 4 (IP_TUNNEL_RECURSION_LIMIT) to prevent overflow. Add recursion detection using dev_xmit_recursion helpers directly in iptunnel_xmit() and ip6tunnel_xmit() to cover all IPv4/IPv6 tunnel paths including UDP encapsulated tunnels (VXLAN, Geneve, etc.). Move dev_xmit_recursion helpers from net/core/dev.h to public header include/linux/netdevice.h so they can be used by tunnel code. BUG: KASAN: stack-out-of-bounds in blake2s.constprop.0+0xe7/0x160 Write of size 32 at addr ffff88810033fed0 by task kworker/0:1/11 Workqueue: mld mld_ifc_work Call Trace: <TASK> __build_flow_key.constprop.0 (net/ipv4/route.c:515) ip_rt_update_pmtu (net/ipv4/route.c:1073) iptunnel_xmit (net/ipv4/ip_tunnel_core.c:84) ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847) gre_tap_xmit (net/ipv4/ip_gre.c:779) dev_hard_start_xmit (net/core/dev.c:3887) sch_direct_xmit (net/sched/sch_generic.c:347) __dev_queue_xmit (net/core/dev.c:4802) bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312) bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279) bond_start_xmit (drivers/net/bonding/bond_main.c:5530) dev_hard_start_xmit (net/core/dev.c:3887) __dev_queue_xmit (net/core/dev.c:4841) ip_finish_output2 (net/ipv4/ip_output.c:237) ip_output (net/ipv4/ip_output.c:438) iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86) gre_tap_xmit (net/ipv4/ip_gre.c:779) dev_hard_start_xmit (net/core/dev.c:3887) sch_direct_xmit (net/sched/sch_generic.c:347) __dev_queue_xmit (net/core/dev.c:4802) bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312) bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279) bond_start_xmit (drivers/net/bonding/bond_main.c:5530) dev_hard_start_xmit (net/core/dev.c:3887) __dev_queue_xmit (net/core/dev.c:4841) ip_finish_output2 (net/ipv4/ip_output.c:237) ip_output (net/ipv4/ip_output.c:438) iptunnel_xmit (net/ipv4/ip_tunnel_core.c:86) ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847) gre_tap_xmit (net/ipv4/ip_gre.c:779) dev_hard_start_xmit (net/core/dev.c:3887) sch_direct_xmit (net/sched/sch_generic.c:347) __dev_queue_xmit (net/core/dev.c:4802) bond_dev_queue_xmit (drivers/net/bonding/bond_main.c:312) bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5279) bond_start_xmit (drivers/net/bonding/bond_main.c:5530) dev_hard_start_xmit (net/core/dev.c:3887) __dev_queue_xmit (net/core/dev.c:4841) mld_sendpack mld_ifc_work process_one_work worker_thread </TASK>
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于隧道发送函数缺少发送递归限制，可能导致无限递归和内核堆栈溢出。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 745e20f1b626b1be4b100af5d4bf7b3439392f8f ~ 834c4f645726a25fd71ea50cdfb5c135f8f95d85 -
Linux Linux 2.6.37 -

II. Public POCs for CVE-2026-23276

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III. Intelligence Information for CVE-2026-23276

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Patches & Fixes for CVE-2026-23276 (4)

Same Patch Batch · Linux · 2026-03-20 · 8 CVEs total

CVE-2026-23278 7.8 HIGH netfilter: nf_tables: always walk all pending catchall elements
CVE-2026-23275 7.8 HIGH io_uring: ensure ctx->rings is stable for task work flags manipulation
CVE-2026-23274 7.8 HIGH netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels
CVE-2026-23273 7.8 HIGH macvlan: observe an RCU grace period in macvlan_common_newlink() error path
CVE-2026-23272 7.8 HIGH netfilter: nf_tables: unconditionally bump set->nelems before insertion
CVE-2026-23271 7.8 HIGH perf: Fix __perf_event_overflow() vs perf_remove_from_context() race
CVE-2026-23277 net/sched: teql: fix NULL pointer dereference in iptunnel_xmit on TEQL slave xmit

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-23276

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