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NVD / CVE Program· CNA Linux

CVE-2024-49940: l2tp: prevent possible tunnel refcount underflow

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.32% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 24256415d18695b46da06c93135f5b51c548b950, 3.17, 3.3.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 24256415d18695b46da06c93135f5b51c548b950, 3.17, 3.3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Oct 21, 2024
Updated
Oct 30, 2026
EPSS
0.3% · 25th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · Linux
7.8
2.3 point gap

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2024-49940

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernelbefore 6.11.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • b102bfc2a90d14f342580285782a9a51c74f7369, 10c15ddabbcf888922adbdd44ca3fecf6eab19d9, 8d1c650d452c53fcb3f02a7b1d772741639f89a4, 12b5fb58ac993c24210cf8cbc72d407d3a4e6490, aef37401b467a0b1a9517c69924a1d66937e0789, 4.15affected
    • 3953ae7b218df4d1e544b98a393666f9ae58a78c and later · before aa7132362e79abc4f2add4d8657dd1679341edc5affected · git
    • 3953ae7b218df4d1e544b98a393666f9ae58a78c and later · before 98691b2e28a6c3dac0680914493d54c77f215755affected · git
    • 3953ae7b218df4d1e544b98a393666f9ae58a78c and later · before f7415e60c25a6108cd7955a20b2e66b6251ffe02affected · git
    • 3953ae7b218df4d1e544b98a393666f9ae58a78c and later · before 24256415d18695b46da06c93135f5b51c548b950affected · git
    • 3.2.99 and later · before 3.3affected · semver
    • 3.16.54 and later · before 3.17affected · semver
    • 4.4.225 and later · before 4.5affected · semver
    • 4.9.225 and later · before 4.10affected · semver
    • 4.14.182 and later · before 4.15affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.11.4-16.11.4-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2024-49930Oct 21, 2024 · wifi: ath11k: fix array out-of-bound access in SoC stats
    31Monitor
  • ← EarlierCVE-2024-49938Oct 21, 2024 · wifi: ath9k_htc: Use __skb_set_length() for resetting urb before resubmit
    22Monitor
  • Later →CVE-2024-49944Oct 21, 2024 · sctp: set sk_state back to CLOSED if autobind fails in sctp_listen_start
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux24256415d18695b46da06c93135f5b51c548b950Vendor (CNA)
Linux Linux3.17Vendor (CNA)
Linux Linux3.3Vendor (CNA)
Linux Linux4.10Vendor (CNA)
Linux Linux4.15Vendor (CNA)
Linux Linux4.5Vendor (CNA)
Linux Linux98691b2e28a6c3dac0680914493d54c77f215755Vendor (CNA)
Linux Linuxaa7132362e79abc4f2add4d8657dd1679341edc5Vendor (CNA)
Linux Linuxf7415e60c25a6108cd7955a20b2e66b6251ffe02Vendor (CNA)
debian:linux6.11.4-1 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records