Mozilla Firefox CSS Letter-Spacing Heap Overflow Vulnerability

Risk: High
Local: Yes
Remote: Yes
CWE: CWE-189

CVSS Base Score: 9.3/10
Impact Subscore: 10/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

ZDI-06-010: Mozilla Firefox CSS Letter-Spacing Heap Overflow Vulnerability April 13, 2006 -- CVE ID: CVE-2006-1730 -- Affected Vendor: Mozilla -- Affected Products: Mozilla 1.7.x and below Firefox 1.5.x and below -- TippingPoint(TM) IPS Customer Protection: TippingPoint IPS customers have been protected against this vulnerability since January 31, 2006 by Digital Vaccine protection filter ID 4097. For further product information on the TippingPoint IPS: -- Vulnerability Details: This vulnerability allows attackers to execute arbitrary code on vulnerable installations of the Mozilla/Firefox web browser. User interaction is required to exploit this vulnerability in that the target must visit a malicious page. The specific flaw is due to incorrect handling of the CSS "letter-spacing" element. By specifying a large number, an attacker can overflow an integer used during memory allocation. The under-allocated buffer is later used to store user-supplied data leading to an exploitable heap overflow. -- Vendor Response: Mozilla has issued an update to correct this vulnerability. Details are available at: -- Disclosure Timeline: 2006.01.31 - Vulnerability reported to vendor 2006.01.31 - Digital Vaccine released to TippingPoint customers 2006.04.13 - Coordinated public release of advisory -- Credit: This vulnerability was discovered by an anonymous researcher. -- About the Zero Day Initiative (ZDI): Established by TippingPoint, a division of 3Com, The Zero Day Initiative (ZDI) represents a best-of-breed model for rewarding security researchers for responsibly disclosing discovered vulnerabilities. Researchers interested in getting paid for their security research through the ZDI can find more information and sign-up at: The ZDI is unique in how the acquired vulnerability information is used. 3Com does not re-sell the vulnerability details or any exploit code. Instead, upon notifying the affected product vendor, 3Com provides its customers with zero day protection through its intrusion prevention technology. Explicit details regarding the specifics of the vulnerability are not exposed to any parties until an official vendor patch is publicly available. Furthermore, with the altruistic aim of helping to secure a broader user base, 3Com provides this vulnerability information confidentially to security vendors (including competitors) who have a vulnerability protection or mitigation product.

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