CVE-2010-1099 in Safari
Summary
by MITRE
Integer overflow in Apple Safari allows remote attackers to bypass intended port restrictions on outbound TCP connections via a port number outside the range of the unsigned short data type, as demonstrated by a value of 65561 for TCP port 25.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability described in CVE-2010-1099 represents a critical integer overflow flaw within Apple Safari web browser that fundamentally compromises network security controls. This issue arises from improper handling of port numbers during TCP connection establishment, creating a pathway for malicious actors to circumvent network access controls that are typically enforced through port restriction mechanisms. The vulnerability specifically targets the unsigned short data type which has a maximum value of 65535, yet the browser fails to properly validate port numbers exceeding this limit, allowing attackers to manipulate connection parameters through crafted values.
The technical exploitation of this vulnerability occurs through the manipulation of TCP port numbers in network connection requests. When Safari processes outbound TCP connections, it does not adequately validate that port numbers fall within the acceptable range for the unsigned short data type, which spans from 0 to 65535. This allows an attacker to specify a port number such as 65561, which when processed through the integer overflow mechanism effectively wraps around to a value within the valid range, thereby bypassing the intended port restriction policies. The flaw specifically demonstrates how a value of 65561 can be used to gain access to TCP port 25, which is typically restricted due to its association with SMTP services and potential for abuse.
This vulnerability presents significant operational impact as it undermines fundamental network security controls that organizations rely upon to protect their systems from unauthorized access. The bypass of port restrictions means that attackers can potentially establish connections to services that should normally be blocked or restricted, particularly those that are commonly targeted for exploitation such as email servers, file transfer protocols, and other network services. The implications extend beyond simple port access, as this vulnerability could enable more sophisticated attacks including port scanning, service enumeration, and potential exploitation of vulnerable services that are typically protected by network segmentation and firewall rules.
The vulnerability maps directly to CWE-190, which describes integer overflow and underflow conditions in software systems, and aligns with ATT&CK technique T1071.004 for application layer protocol usage, specifically targeting web browser security controls. Organizations implementing network security measures that rely on port-based restrictions for protecting against unauthorized network access are particularly vulnerable to this type of attack, as the flaw effectively neutralizes these controls through mathematical manipulation of data types. The attack vector demonstrates how seemingly benign input validation can create critical security gaps when dealing with data type boundaries and integer arithmetic operations in network applications.
Mitigation strategies for this vulnerability require immediate patching of affected Safari versions and implementation of additional network-level controls to monitor and restrict unusual port connection patterns. System administrators should deploy network monitoring solutions that can detect anomalous port usage patterns and implement strict firewall rules that prevent connections to sensitive ports from unexpected sources. Additionally, organizations should consider implementing application whitelisting policies that restrict which applications can make outbound network connections, and conduct regular security assessments to identify similar integer overflow vulnerabilities in other network applications and browser components. The remediation process must also include comprehensive testing of network security controls to ensure that port restrictions are properly enforced regardless of the specific port number values used in connection requests.