CVE-2024-49940

Local kernel compromise via L2TP refcount underflow

Published Oct 21, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel L2TP allows local users to read or alter kernel memory or crash the system through colliding session IDs. l2tp_session_create assigns session->tunnel before l2tp_session_register increments the tunnel reference, so failed or racing registration lets l2tp_session_free decrement an unacquired reference and prematurely free the tunnel. An unprivileged local user can reach the socket path, and concurrent session creation and teardown can trigger the dangling tunnel access without user interaction.

CVSS severity7.8
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel L2TP allows local users to read or alter kernel memory or crash the system through colliding session IDs. l2tp_session_create assigns session->tunnel before l2tp_session_register increments the tunnel reference, so failed or racing registration lets l2tp_session_free decrement an unacquired reference and prematurely free the tunnel. An unprivileged local user can reach the socket path, and concurrent session creation and teardown can trigger the dangling tunnel access without user interaction.

The record

CVE
CVE-2024-49940
Published
Oct 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10c15ddabbcf888922adbdd44ca3fecf6eab19d9
  2. Affected versionversion=12b5fb58ac993c24210cf8cbc72d407d3a4e6490
  3. Affected versionversion=3.16.54 <3.17
  4. Affected versionversion=3.2.99 <3.3
  5. Affected versionversion=3953ae7b218df4d1e544b98a393666f9ae58a78c <24256415d18695b46da06c93135f5b51c548b950
  6. Affected versionversion=3953ae7b218df4d1e544b98a393666f9ae58a78c <f7415e60c25a6108cd7955a20b2e66b6251ffe02
  7. Affected versionversion=4.14.182 <4.15
  8. Affected versionversion=4.15
  9. Affected versionversion=4.4.225 <4.5
  10. Affected versionversion=4.9.225 <4.10
  11. Affected versionversion=8d1c650d452c53fcb3f02a7b1d772741639f89a4
  12. Affected versionversion=aef37401b467a0b1a9517c69924a1d66937e0789
  13. Affected versionversion=b102bfc2a90d14f342580285782a9a51c74f7369

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=10c15ddabbcf888922adbdd44ca3fecf6eab19d9; version=12b5fb58ac993c24210cf8cbc72d407d3a4e6490; version=3.16.54 <3.17; version=3.2.99 <3.3; version=3953ae7b218df4d1e544b98a393666f9ae58a78c <24256415d18695b46da06c93135f5b51c548b950; version=3953ae7b218df4d1e544b98a393666f9ae58a78c <f7415e60c25a6108cd7955a20b2e66b6251ffe02; version=4.14.182 <4.15; version=4.15; version=4.4.225 <4.5; version=4.9.225 <4.10; version=8d1c650d452c53fcb3f02a7b1d772741639f89a4; version=aef37401b467a0b1a9517c69924a1d66937e0789; version=b102bfc2a90d14f342580285782a9a51c74f7369

Published CVSS scores

7.8Linux kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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