CVE-2023-27567Network attack vector

Kernel crash via diverted port-zero TCP packet

Published Mar 3, 2023 · Updated Mar 6, 2025

Denial of service in the OpenBSD 7.2 TCP stack allows remote attackers to crash the kernel with a TCP packet sent to port 0. When a PF divert-to rule redirects the packet, tcp_input can bind an accept socket on port 0, violating a kernel assertion that assumes a listening port is never zero. The packet must match an enabled divert-to rule; successful exploitation triggers a kernel panic and interrupts the host.

CVSS severity7.5
High
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the OpenBSD 7.2 TCP stack allows remote attackers to crash the kernel with a TCP packet sent to port 0. When a PF divert-to rule redirects the packet, tcp_input can bind an accept socket on port 0, violating a kernel assertion that assumes a listening port is never zero. The packet must match an enabled divert-to rule; successful exploitation triggers a kernel panic and interrupts the host.

The record

CVE
CVE-2023-27567
Published
Mar 3, 2023
Updated
Mar 6, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 6, 2025Record 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS: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.

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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