// For flags

CVE-2023-6534

TCP spoofing vulnerability in pf(4)

Severity Score

7.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

In versions of FreeBSD 14.0-RELEASE before 14-RELEASE-p2, FreeBSD 13.2-RELEASE before 13.2-RELEASE-p7 and FreeBSD 12.4-RELEASE before 12.4-RELEASE-p9, the pf(4) packet filter incorrectly validates TCP sequence numbers. This could allow a malicious actor to execute a denial-of-service attack against hosts behind the firewall.

En las versiones de FreeBSD 14.0-RELEASE anteriores a 14-RELEASE-p2, FreeBSD 13.2-RELEASE anteriores a 13.2-RELEASE-p7 y FreeBSD 12.4-RELEASE anteriores a 12.4-RELEASE-p9, el filtro de paquetes pf(4) valida incorrectamente los números de secuencia TCP. Esto podría permitir que un actor malintencionado ejecute un ataque de denegación de servicio contra hosts detrás del firewall.

As part of its stateful TCP connection tracking implementation, pf performs sequence number validation on inbound packets. This makes it difficult for a would-be attacker to spoof the sender and inject packets into a TCP stream, since crafted packets must contain sequence numbers which match the current connection state to avoid being rejected by the firewall. A bug in the implementation of sequence number validation means that the sequence number is not in fact validated, allowing an attacker who is able to impersonate the remote host and guess the connection's port numbers to inject packets into the TCP stream. An attacker can, with relatively little effort, inject packets into a TCP stream destined to a host behind a pf firewall. This could be used to implement a denial-of-service attack for hosts behind the firewall, for example by sending TCP RST packets to the host.

*Credits: Yuxiang Yang, Ao Wang, Xuewei Feng, Qi Li and Ke Xu from Tsinghua University
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2023-12-05 CVE Reserved
  • 2023-12-05 CVE Published
  • 2025-02-13 CVE Updated
  • 2025-04-15 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Freebsd
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Freebsd
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12.4
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-
Affected
Freebsd
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Freebsd
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12.4
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p1
Affected
Freebsd
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Freebsd
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12.4
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p2
Affected
Freebsd
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Freebsd
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12.4
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p3
Affected
Freebsd
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Freebsd
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12.4
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p4
Affected
Freebsd
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Freebsd
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12.4
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p5
Affected
Freebsd
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Freebsd
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12.4
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p6
Affected
Freebsd
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Freebsd
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12.4
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p7
Affected
Freebsd
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Freebsd
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12.4
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p8
Affected
Freebsd
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Freebsd
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12.4
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rc2-p1
Affected
Freebsd
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Freebsd
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12.4
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rc2-p2
Affected
Freebsd
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Freebsd
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13.2
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-
Affected
Freebsd
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Freebsd
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13.2
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p1
Affected
Freebsd
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Freebsd
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13.2
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p2
Affected
Freebsd
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Freebsd
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13.2
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p3
Affected
Freebsd
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Freebsd
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13.2
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p4
Affected
Freebsd
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Freebsd
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13.2
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p5
Affected
Freebsd
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Freebsd
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13.2
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p6
Affected
Freebsd
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Freebsd
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14.0
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-
Affected
Freebsd
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Freebsd
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14.0
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beta5
Affected
Freebsd
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Freebsd
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14.0
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p1
Affected
Freebsd
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Freebsd
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14.0
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rc3
Affected
Freebsd
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Freebsd
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14.0
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rc4-p1
Affected