CVE-2008-0438 in sIFR
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the font rendering functionality in Novemberborn sIFR 2.0.2 allows remote attackers to inject arbitrary web script or HTML via the txt parameter to a Flash (SWF) file, as demonstrated by fonts/FuturaLt.swf.
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Analysis
by VulDB Data Team • 06/01/2025
The vulnerability identified as CVE-2008-0438 represents a critical cross-site scripting flaw within the sIFR 2.0.2 library, a popular web tool for rendering text using flash fonts. This issue specifically targets the font rendering functionality that enables websites to display custom typography through flash-based solutions. The vulnerability arises from inadequate input validation and sanitization within the sIFR implementation, creating a pathway for malicious actors to inject arbitrary code into web pages that utilize this technology. The flaw manifests when the application fails to properly escape or filter user-supplied data passed through the txt parameter to flash files, particularly affecting the FuturaLt.swf font file within the fonts directory structure.
The technical exploitation of this vulnerability occurs through the manipulation of the txt parameter that gets passed to the Flash SWF file during font rendering operations. When a user visits a webpage utilizing sIFR 2.0.2 with maliciously crafted input in the txt parameter, the flash component processes this unvalidated data without proper sanitization measures. This creates a persistent cross-site scripting condition where attacker-controlled scripts can execute within the context of the victim's browser session. The vulnerability is particularly concerning because it operates at the intersection of flash-based rendering and web application security, exploiting the trust relationship between the browser and the flash plugin to execute malicious code. According to CWE standards, this maps to CWE-79: Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to sanitize user input that gets reflected back to users.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious sites. The vulnerability affects any website implementing sIFR 2.0.2 with vulnerable flash font files, making it particularly dangerous in environments where user-generated content is accepted or where the application does not properly validate input parameters. The attack vector is particularly insidious because it requires minimal user interaction beyond visiting a compromised webpage, and the malicious scripts can persist across multiple page views as long as the vulnerable sIFR implementation remains active. This vulnerability aligns with ATT&CK technique T1566.001: Phishing, as attackers can craft malicious web pages that exploit this XSS flaw to deliver payloads to unsuspecting users.
Mitigation strategies for this vulnerability require immediate remediation through software updates to sIFR 2.0.3 or later versions which address the input validation issues. Organizations should implement comprehensive input sanitization measures that properly escape all user-supplied data before it is processed by the sIFR library, particularly focusing on the txt parameter handling. Additionally, implementing proper content security policies and output encoding techniques can provide defense-in-depth protection against similar vulnerabilities. The vulnerability demonstrates the importance of validating and sanitizing all inputs, especially those processed by third-party libraries, and highlights the need for regular security assessments of web applications that utilize flash-based technologies. Given the age of this vulnerability and the deprecation of flash technology, organizations should prioritize migrating away from sIFR implementations to modern CSS-based typography solutions that eliminate the attack surface entirely.