Linux Kernel up to 6.18.9 macvlan_common_newlink use after free

CVSS Meta Temp Score
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CTI Interest Score
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7.7$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.9. It has been declared as critical. This impacts the function macvlan_common_newlink. Such manipulation leads to use after free. This vulnerability is listed as CVE-2026-23209. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.9. It has been rated as critical. Affected by this issue is the function macvlan_common_newlink. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: macvlan: fix error recovery in macvlan_common_newlink() valis provided a nice repro to crash the kernel: ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2 ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20 ping -c1 -I p1 1.2.3.4 He also gave a very detailed analysis: <quote valis> The issue is triggered when a new macvlan link is created with MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan port and register_netdevice() called from macvlan_common_newlink() fails (e.g. because of the invalid link name). In this case macvlan_hash_add_source is called from macvlan_change_sources() / macvlan_common_newlink(): This adds a reference to vlan to the port's vlan_source_hash using macvlan_source_entry. vlan is a pointer to the priv data of the link that is being created. When register_netdevice() fails, the error is returned from macvlan_newlink() to rtnl_newlink_create(): if (ops->newlink) err = ops->newlink(dev, &params, extack); else err = register_netdevice(dev); if (err < 0) { free_netdev(dev); goto out; } and free_netdev() is called, causing a kvfree() on the struct net_device that is still referenced in the source entry attached to the lower device's macvlan port. Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlan_forward_source(). </quote valis> With all that, my fix is to make sure we call macvlan_flush_sources() regardless of @create value whenever "goto destroy_macvlan_port;" path is taken. Many thanks to valis for following up on this issue.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-23209 since 01/13/2026. The exploitation is known to be easy. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 05/06/2026).

The vulnerability scanner Nessus provides a plugin with the ID 299121 (Linux Distros Unpatched Vulnerability : CVE-2026-23209), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.10.250, 5.15.200, 6.1.163, 6.6.124, 6.12.70 or 6.18.10 eliminates this vulnerability. Applying the patch da5c6b8ae47e414be47e5e04def15b25d5c962dc/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a/c43d0e787cbba569ec9d11579ed370b50fab6c9c/11ba9f0dc865136174cb98834280fb21bbc950c7/986967a162142710076782d5b93daab93a892980/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66/f8db6475a83649689c087a8f52486fcc53e627e9 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (299121) and CERT Bund (WID-SEC-2026-0421). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.7

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 299121
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-23209

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.250/5.15.200/6.1.163/6.6.124/6.12.70/6.18.10
Patch: da5c6b8ae47e414be47e5e04def15b25d5c962dc/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a/c43d0e787cbba569ec9d11579ed370b50fab6c9c/11ba9f0dc865136174cb98834280fb21bbc950c7/986967a162142710076782d5b93daab93a892980/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66/f8db6475a83649689c087a8f52486fcc53e627e9

Timelineinfo

01/13/2026 CVE reserved
02/14/2026 +32 days Advisory disclosed
02/14/2026 +0 days VulDB entry created
05/06/2026 +81 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-23209 (🔒)
GCVE (CVE): GCVE-0-2026-23209
GCVE (VulDB): GCVE-100-346058
CERT Bund: WID-SEC-2026-0421 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 02/14/2026 18:10
Updated: 05/06/2026 04:56
Changes: 02/14/2026 18:10 (58), 02/14/2026 19:43 (1), 02/15/2026 10:38 (2), 02/19/2026 14:44 (1), 03/19/2026 07:23 (11), 05/06/2026 04:56 (7)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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