The PKI functionality in Mac OS X 10.2.8 and 10.3.2 allows remote attackers to cause a denial of service (service crash) via malformed ASN.1 sequences.
Mac OS X versions 10.2.8 and 10.3.2 are vulnerable to a denial-of-service (DoS) attack due to a flaw in their Public Key Infrastructure (PKI) implementation. Attackers can remotely crash the system by sending specially crafted, malformed ASN.1 sequences, rendering the affected system unavailable.
Step 1: Target Identification: The attacker identifies a Mac OS X system running versions 10.2.8 or 10.3.2.
Step 2: Payload Creation: The attacker crafts a malicious ASN.1 sequence. This sequence is designed to be malformed, triggering a vulnerability in the PKI parsing logic.
Step 3: Payload Delivery: The attacker sends the malicious ASN.1 sequence to the vulnerable system. This could be achieved through various means, such as a network connection, email, or a file.
Step 4: PKI Processing: The PKI component on the target system attempts to parse the malicious ASN.1 sequence.
Step 5: Vulnerability Trigger: Due to the malformed sequence, the parsing process encounters an error, such as an unhandled exception or an attempt to access invalid memory.
Step 6: Denial of Service: The error causes the PKI service to crash, leading to a denial of service. This may result in the system becoming unresponsive or rebooting.
The vulnerability stems from inadequate input validation within the PKI component's ASN.1 parsing routines. Specifically, the software fails to properly handle malformed ASN.1 sequences, leading to a service crash. The root cause is likely an unhandled exception or an attempt to access memory outside of allocated bounds when processing the corrupted data. This could manifest as a null pointer dereference, an integer overflow, or a similar error during the parsing process. The lack of proper bounds checking or error handling allows the attacker to trigger a fatal error within the PKI service, resulting in a system-wide crash.