CVE-2024-49940
Description
A flaw was found in the Linux kernel's implementation of the Layer 2 Tunneling Protocol (L2TP). A race condition during the creation and registration of L2TP sessions can lead to a tunnel reference count underflow. This issue allows a local attacker with low privileges to cause a Denial of Service (DoS) by making the system unstable or unresponsive.
Mitigation
To mitigate this issue, prevent the `l2tp_core` kernel module from loading. This can be achieved by blacklisting the module.
To temporarily unload the module (if not in use):
`# modprobe -r l2tp_core`
To permanently blacklist the module, create a configuration file:
`# echo "blacklist l2tp_core" >> /etc/modprobe.d/blacklist-l2tp.conf`
A system reboot or module reload is required for the change to take full effect. Disabling this module may impact L2TP VPN functionality.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | 7.8 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | Low | Low | Low |
| Privileges Required | Low | Low | Low |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | High |
| Integrity Impact | None | None | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality
Technical Impact: Modify Application Data; Read Application Data
If a released resource is subsequently reused or reallocated, then an attempt to use the original resource might allow access to sensitive data that is associated with a different user or entity.
Other,Availability
Technical Impact: Other; DoS: Crash, Exit, or Restart
When a resource is released it might not be in an expected state, later attempts to access the resource may lead to resultant errors that may lead to a crash.
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