Linux Kernel up to 6.11.2 l2tp_session_free reference count

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.11.2. Affected is the function l2tp_session_free. Performing a manipulation results in reference count. This vulnerability is reported as CVE-2024-49940. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.11.2. It has been classified as problematic. This affects the function l2tp_session_free. The manipulation with an unknown input leads to a reference count vulnerability. CWE is classifying the issue as CWE-911. The product uses a reference count to manage a resource, but it does not update or incorrectly updates the reference count. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: l2tp: prevent possible tunnel refcount underflow When a session is created, it sets a backpointer to its tunnel. When the session refcount drops to 0, l2tp_session_free drops the tunnel refcount if session->tunnel is non-NULL. However, session->tunnel is set in l2tp_session_create, before the tunnel refcount is incremented by l2tp_session_register, which leaves a small window where session->tunnel is non-NULL when the tunnel refcount hasn't been bumped. Moving the assignment to l2tp_session_register is trivial but l2tp_session_create calls l2tp_session_set_header_len which uses session->tunnel to get the tunnel's encap. Add an encap arg to l2tp_session_set_header_len to avoid using session->tunnel. If l2tpv3 sessions have colliding IDs, it is possible for l2tp_v3_session_get to race with l2tp_session_register and fetch a session which doesn't yet have session->tunnel set. Add a check for this case.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2024-49940 since 10/21/2024. The exploitability is told to be difficult. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 216030 (EulerOS 2.0 SP12 : kernel (EulerOS-SA-2025-1176)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.11.3 eliminates this vulnerability. Applying the patch f7415e60c25a/24256415d186 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 (216030) and CERT Bund (WID-SEC-2024-3251). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• NetApp StorageGRID
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• Kyocera Printer
• NetApp AFF
• NetApp ActiveIQ Unified Manager
• SUSE openSUSE
• IBM Security Guardium
• RESF Rocky Linux
• Dell NetWorker
• Dell Avamar
• IBM QRadar SIEM
• NetApp FAS
• SolarWinds Security Event Manager
• Dell PowerProtect Data Domain
• Open Source Linux Kernel
• Dell PowerScale OneFS

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.11.0
• 6.11.1
• 6.11.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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