CVE-2012-0441 in Firefox
Summary
by MITRE
The ASN.1 decoder in the QuickDER decoder in Mozilla Network Security Services (NSS) before 3.13.4, as used in Firefox 4.x through 12.0, Firefox ESR 10.x before 10.0.5, Thunderbird 5.0 through 12.0, Thunderbird ESR 10.x before 10.0.5, and SeaMonkey before 2.10, allows remote attackers to cause a denial of service (application crash) via a zero-length item, as demonstrated by (1) a zero-length basic constraint or (2) a zero-length field in an OCSP response.
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Analysis
by VulDB Data Team • 10/21/2024
The vulnerability identified as CVE-2012-0441 represents a critical denial of service flaw within the Network Security Services (NSS) library that powers Mozilla's security infrastructure. This issue specifically affects the QuickDER decoder component responsible for parsing ASN.1 encoded data structures commonly used in cryptographic protocols and certificate handling. The vulnerability manifests when the decoder encounters zero-length items in ASN.1 structures, particularly in basic constraints within X.509 certificates or fields within OCSP responses, leading to application crashes and system instability.
The technical flaw stems from inadequate input validation within the ASN.1 decoding process where the QuickDER parser fails to properly handle zero-length elements in encoded data structures. This weakness falls under CWE-129, which addresses improper validation of length values, and specifically relates to CWE-476, indicating a null pointer dereference scenario that occurs when the decoder attempts to process malformed ASN.1 structures containing zero-length items. The vulnerability exploits the fundamental assumption that ASN.1 structures will contain valid data elements, creating a path where malformed input directly translates to memory access violations and subsequent application termination.
Operationally, this vulnerability presents significant risk to organizations relying on affected Mozilla products including Firefox browsers, Thunderbird email clients, and SeaMonkey web suites. Attackers can remotely trigger application crashes by crafting malicious certificates or OCSP responses containing zero-length ASN.1 items, effectively creating a denial of service condition that disrupts legitimate user sessions and potentially impacts business continuity. The attack surface extends across multiple Mozilla products and versions, making it particularly dangerous as defenders must account for various client implementations. The vulnerability's impact aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a classic example of a resource exhaustion attack that consumes application resources through malformed input processing.
Mitigation strategies should focus on immediate patch deployment for all affected NSS versions, specifically upgrading to NSS 3.13.4 or later where the vulnerability has been addressed through improved input validation and proper handling of zero-length ASN.1 elements. Organizations should also implement network monitoring to detect unusual certificate or OCSP response patterns that might indicate exploitation attempts. Additional defensive measures include configuring application firewalls to filter suspicious ASN.1 data, implementing certificate pinning where appropriate, and establishing incident response procedures for handling potential denial of service scenarios. The fix typically involves strengthening the ASN.1 decoder to properly validate element lengths before processing and implementing robust error handling that prevents application crashes from malformed input structures.