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🛡️ CVE-2024-49940 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

l2tp: prevent possible tunnel refcount underflow

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.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

CVE-2024-49940 is recorded against 2 packages.

  • kernel (from 4.15.0 up to 6.11.3)
  • linux-kernel (fixed in 6.11.3)

Timeline and source

Published on 21 October 2024 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

Other advisories for this package

kernel has other advisories on record. If you are patching this one, these are worth checking on the same host:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2024-10-21
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 4.15.0 6.11.3
linux-kernel — 6.11.3

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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