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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.18% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 2.6.36, 6f1a9140ecda3baba3d945b9a6155af4268aafc4, 834c4f645726a25fd71ea50cdfb5c135f8f95d85; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 2.6.36, 6f1a9140ecda3baba3d945b9a6155af4268aafc4, 834c4f645726a25fd71ea50cdfb5c135f8f95d85; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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>

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Mar 20, 2026
Updated
Nov 5, 2026
EPSS
0.1% · 7th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.35.9 and later · before 2.6.36
  • linux linux kernel2.6.37 and later · before 6.12.78
  • linux linux kernel6.13 and later · before 6.18.19
  • linux linux kernel6.19 and later · before 6.19.9
  • linux linux kernel7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 3f266b04185de51d8e6446eb1fccec3b5e7ce575, 2.6.37affected
    • 745e20f1b626b1be4b100af5d4bf7b3439392f8f and later · before da5f0166cef3d4285ddbb1b638661263fc03ee92affected · git
    • 745e20f1b626b1be4b100af5d4bf7b3439392f8f and later · before 834c4f645726a25fd71ea50cdfb5c135f8f95d85affected · git
    • 745e20f1b626b1be4b100af5d4bf7b3439392f8f and later · before 8a57deeb256069f262957d8012418559ff66c385affected · git
    • 745e20f1b626b1be4b100af5d4bf7b3439392f8f and later · before b56b8d19bd05e2a8338385c770bc2b60590bc81eaffected · git
    • 745e20f1b626b1be4b100af5d4bf7b3439392f8f and later · before 6f1a9140ecda3baba3d945b9a6155af4268aafc4affected · git
    • 2.6.35.9 and later · before 2.6.36affected · semver
    • before 2.6.37not affected · semver
    • 6.6.160 and later · up to and including 6.6.*not affected · semver
    • 6.12.78 and later · up to and including 6.12.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.10-16.19.10-1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_19before 1-150700.15.3.41-150700.15.3.4
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7-RT_Update_18before 1-150700.1.5.11-150700.1.5.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-64kbbefore 6.4.0-150700.53.73.26.4.0-150700.53.73.2
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-defaultbefore 6.4.0-150700.53.73.26.4.0-150700.53.73.2
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-default-basebefore 6.4.0-150700.53.73.2.150700.17.41.46.4.0-150700.53.73.2.150700.17.41.4
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-sourcebefore 6.4.0-150700.53.73.16.4.0-150700.53.73.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-zfcpdumpbefore 6.4.0-150700.53.73.26.4.0-150700.53.73.2
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-docsbefore 6.4.0-150700.53.73.16.4.0-150700.53.73.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-obs-buildbefore 6.4.0-150700.53.73.26.4.0-150700.53.73.2
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-symsbefore 6.4.0-150700.53.73.16.4.0-150700.53.73.1
SUSE:Linux Enterprise Module for Public Cloud 15 SP7kernel-azurebefore 6.4.0-150700.53.73.26.4.0-150700.53.73.2
SUSE:Linux Micro 6.1kernel-defaultbefore 6.4.0-51.16.4.0-51.1
SUSE:Linux Micro 6.1kernel-kvmsmallbefore 6.4.0-51.16.4.0-51.1
SUSE:Linux Micro 6.1kernel-rtbefore 6.4.0-51.16.4.0-51.1
SUSE:Linux Micro 6.1kernel-sourcebefore 6.4.0-51.16.4.0-51.1
SUSE:Linux Micro 6.1kernel-source-rtbefore 6.4.0-51.16.4.0-51.1
SUSE:Real Time Module 15 SP7kernel-rtbefore 6.4.0-150700.7.67.16.4.0-150700.7.67.1
SUSE:Real Time Module 15 SP7kernel-source-rtbefore 6.4.0-150700.7.67.16.4.0-150700.7.67.1
SUSE:Real Time Module 15 SP7kernel-syms-rtbefore 6.4.0-150700.7.67.16.4.0-150700.7.67.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-23274Mar 20, 2026 · netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels
    31Monitor
  • ← EarlierCVE-2026-23275Mar 20, 2026 · io_uring: ensure ctx->rings is stable for task work flags manipulation
    31Monitor
  • Later →CVE-2026-23277Mar 20, 2026 · net/sched: teql: fix NULL pointer dereference in iptunnel_xmit on TEQL slave xmit
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2.6.36Vendor (CNA)
Linux Linux6f1a9140ecda3baba3d945b9a6155af4268aafc4Vendor (CNA)
Linux Linux834c4f645726a25fd71ea50cdfb5c135f8f95d85Vendor (CNA)
Linux Linux8a57deeb256069f262957d8012418559ff66c385Vendor (CNA)
Linux Linuxb56b8d19bd05e2a8338385c770bc2b60590bc81eVendor (CNA)
Linux Linuxda5f0166cef3d4285ddbb1b638661263fc03ee92Vendor (CNA)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.85-1 · Debian:13Package registry (OSV)
suse:kernel-64kb6.4.0-150700.53.73.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-default6.4.0-51.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-default-base6.4.0-150700.53.73.2.150700.17.41.4 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-docs6.4.0-150700.53.73.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package registry (OSV)
suse:kernel-kvmsmall6.4.0-51.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-livepatch-SLE15-SP7-RT_Update_181-150700.1.5.1 · SUSE:Linux Enterprise Live Patching 15 SP7Package registry (OSV)
suse:kernel-obs-build6.4.0-150700.53.73.2 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package registry (OSV)
suse:kernel-rt6.4.0-51.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-source6.4.0-51.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-source-rt6.4.0-51.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-syms-rt6.4.0-150700.7.67.1 · SUSE:Real Time Module 15 SP7Package registry (OSV)
suse:kernel-zfcpdump6.4.0-150700.53.73.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-4318547 days apartksmbd: fix signededness bug in smb_direct_prepare_negotiation()
    39Monitor
  • CVE-2026-5320297 days apartaccel/ivpu: Fix signed integer truncation in IPC receive
    31Monitor
  • CVE-2026-5326797 days apartnetfilter: nft_ct: bail out on template ct in get eval
    31Monitor
  • CVE-2025-38459238 days apartatm: clip: Fix infinite recursive call of clip_push().
    31Monitor
  • CVE-2026-53395121 days apartnfsd: fix dead ACL conflict guard in nfsd4_create
    30Monitor
  • CVE-2026-4614969 days apartscsi: target: configfs: Bound snprintf() return in tg_pt_gp_members_show()
    28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-674 · Uncontrolled Recursion

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records