CVE-2024-49940

Medium

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.

Package Linux Kernel
Published 2024-10-21
Last modified 2024-11-13
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected versions

Linux kernel versions 3.2.99, 3.16.54, 4.4.225, 4.9.225, 4.14.182, 4.15 and later are affected. Fixed in 6.11.3, 6.12 and their respective stable series.

Affected from
≥ 3.2.99 ≥ 3.16.54 ≥ 4.4.225 ≥ 4.9.225 ≥ 4.14.182 ≥ 4.15
Fixed in
✓ 6.11.3 6.11.x ✓ 6.12

References

The following references provide additional information about CVE-2024-49940 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Frequently asked questions

  • What is CVE-2024-49940?

    CVE-2024-49940 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 3.2.99 onward and has been patched in 6.11.3 and 6.12. CVE-2024-49940 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2024-49940?

    CVE-2024-49940 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2024-49940?

    Yes — CVE-2024-49940 has been patched. Fixed versions include 6.11.3 and 6.12. If you are running Linux kernel 3.2.99 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2024-49940 actively exploited?

    No — CVE-2024-49940 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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