CVE-2023-31436

Local privilege escalation via unchecked MTU-derived lmax

Published Apr 28, 2023 · Updated Oct 21, 2024

Out-of-bounds write in the Linux kernel before 6.2.13 allows local users to crash the system or gain elevated privileges. When TCA_QFQ_LMAX is absent, qfq_change_class uses the device MTU as lmax without applying the explicit-input bounds check, producing an index above QFQ_MAX_INDEX. Exploitation requires local low-privileged access and the ability to configure QFQ; successful abuse can crash the host or execute code with kernel privileges.

CVSS severity7.8
High
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in the Linux kernel before 6.2.13 allows local users to crash the system or gain elevated privileges. When TCA_QFQ_LMAX is absent, qfq_change_class uses the device MTU as lmax without applying the explicit-input bounds check, producing an index above QFQ_MAX_INDEX. Exploitation requires local low-privileged access and the ability to configure QFQ; successful abuse can crash the host or execute code with kernel privileges.

The record

CVE
CVE-2023-31436
Published
Apr 28, 2023
Updated
Oct 21, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 28, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS: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

CWE-787Out-of-bounds Write
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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