CVE-2026-7164: SCTP Buffer Overflow Vulnerability

CVE-2026-7164 Overview

CVE-2026-7164 is a Denial of Service vulnerability in FreeBSD's packet filter (pf) affecting SCTP chunk parameter parsing. Incorrect packet validation allows unbounded recursion when processing specially crafted SCTP packets, eventually resulting in a stack overflow and kernel panic.

Remote attackers can craft malicious packets that cause affected systems to crash. This vulnerability affects any FreeBSD system where pf is configured to process traffic, independent of the configured ruleset, making it particularly dangerous for network infrastructure systems.

Critical Impact
Remote attackers can trigger a kernel panic on any FreeBSD system running pf, causing complete system denial of service without requiring any authentication or specific firewall rules.

Affected Products

FreeBSD systems with pf (packet filter) enabled
Any FreeBSD configuration where pf processes network traffic
Network appliances and firewalls based on FreeBSD pf

Discovery Timeline

2026-04-30 - CVE CVE-2026-7164 published to NVD
2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7164

Vulnerability Analysis

This vulnerability stems from CWE-674 (Uncontrolled Recursion) in the FreeBSD packet filter's SCTP protocol handling. When pf parses SCTP chunk parameters in incoming packets, it fails to implement proper bounds checking on the recursion depth. Maliciously crafted SCTP packets with deeply nested or specially structured chunk parameters trigger unbounded recursive function calls during the parsing routine.

The recursive parsing continues until the kernel stack is exhausted, at which point a stack overflow occurs, resulting in a kernel panic. Since the vulnerability exists in the packet processing path itself rather than in any specific firewall rule evaluation, it affects all systems running pf regardless of their configuration. This makes the attack surface extremely broad for any network-facing FreeBSD system using this packet filter.

Root Cause

The root cause is improper input validation in the SCTP chunk parameter parsing code within pf. The parser lacks recursion depth limits, allowing attackers to construct packets that force the parser into an unbounded recursive loop. This is classified as CWE-674 (Uncontrolled Recursion), where the software does not properly control the amount of recursion that takes place, consuming excessive resources.

Attack Vector

The attack can be conducted remotely over the network by sending specially crafted SCTP packets to any interface monitored by pf. No authentication is required, and the attack works regardless of the firewall ruleset configured. An attacker simply needs network connectivity to the target system.

The vulnerability is exploited by constructing SCTP packets with malformed chunk parameters that trigger recursive parsing. When pf processes these packets at the kernel level, the uncontrolled recursion consumes stack space until a stack overflow triggers a kernel panic, causing immediate system unavailability.

Detection Methods for CVE-2026-7164

Indicators of Compromise

Unexpected system crashes or kernel panics on FreeBSD systems running pf
Crash dumps showing stack overflow in pf SCTP parsing routines
Unusual volume of malformed SCTP traffic targeting the system
Repeated system reboots with kernel panic messages related to stack exhaustion

Detection Strategies

Monitor for kernel panic events with stack traces indicating pf SCTP handling functions
Deploy network intrusion detection signatures for malformed SCTP packets with abnormal chunk structures
Analyze crash dumps for evidence of stack exhaustion in packet filter code paths
Implement traffic analysis to identify unusual SCTP packet patterns targeting FreeBSD systems

Monitoring Recommendations

Enable kernel crash dump collection to capture forensic evidence of exploitation attempts
Configure syslog monitoring for kernel panic messages and system crashes
Deploy network traffic monitoring to baseline normal SCTP traffic and alert on anomalies
Monitor system availability and implement automated alerting for unexpected reboots

How to Mitigate CVE-2026-7164

Immediate Actions Required

Apply the FreeBSD security patch referenced in FreeBSD-SA-26:14.pf immediately
Consider temporarily disabling pf if SCTP traffic is not required until patches can be applied
Implement network-level filtering to block SCTP traffic at perimeter devices if feasible
Ensure system crash dumps are enabled to capture evidence of potential exploitation

Patch Information

FreeBSD has released a security advisory addressing this vulnerability. System administrators should apply the patches referenced in the FreeBSD Security Advisory. Follow standard FreeBSD update procedures using freebsd-update or by rebuilding the kernel from patched sources.

Workarounds

Block SCTP traffic (IP protocol 132) at the network perimeter if SCTP is not required for operations
Implement rate limiting on SCTP traffic at upstream network devices to reduce attack surface
Consider using an alternative packet filter or firewall solution temporarily until patches are applied
Deploy network-level SCTP inspection on external firewalls to filter malformed packets before they reach vulnerable systems

bash

# Block SCTP traffic at network perimeter (example using ipfw as alternative)
ipfw add deny ip from any to any proto 132

# If using upstream firewall, block SCTP protocol
# Protocol 132 = SCTP