CVE-2023-52557Network attack vector

Unauthenticated daemon crash via undersized L2TP AVP

Published Mar 1, 2024 · Updated Aug 2, 2024

Buffer-size calculation error in npppd in OpenBSD 7.3 before errata 016 allows remote attackers to crash the daemon via a malformed L2TP message. The l2tp_subr.c avp_enum function accepts an AVP length below the six-byte header size, then uses that invalid value while parsing or copying attribute data. The target must be running the npppd L2TP service; a crafted unauthenticated network packet interrupts that daemon rather than the entire host.

CVSS severity7.5
High
EPSS probability0.56%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer-size calculation error in npppd in OpenBSD 7.3 before errata 016 allows remote attackers to crash the daemon via a malformed L2TP message. The l2tp_subr.c avp_enum function accepts an AVP length below the six-byte header size, then uses that invalid value while parsing or copying attribute data. The target must be running the npppd L2TP service; a crafted unauthenticated network packet interrupts that daemon rather than the entire host.

The record

CVE
CVE-2023-52557
Published
Mar 1, 2024
Updated
Aug 2, 2024
Vendor
OpenBSD Project
Product
OpenBSD
Classifications
CWE-131, CWE-805, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 1, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 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?

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

  1. Affected versionversion=7.3 <7.3 errata 016
  2. Affected versionversion=7.3 <7.3_errata_016

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenBSD Project · OpenBSDversion=7.3 <7.3 errata 016; version=7.3 <7.3_errata_016

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-131Incorrect Calculation of Buffer Size
CWE-805Buffer Access with Incorrect Length Value
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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