CVE-2011-0556 in Shockwave Player
Summary
by MITRE
The Font Xtra.x32 module in Adobe Shockwave Player before 11.5.9.620 allows attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted PFR1 chunk that leads to an unexpected sign extension and an invalid pointer dereference, a different vulnerability than CVE-2011-0569.
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Analysis
by VulDB Data Team • 01/23/2025
The vulnerability identified as CVE-2011-0556 represents a critical memory corruption flaw within Adobe Shockwave Player's Font Xtra.x32 module. This issue affects versions prior to 11.5.9.620 and demonstrates how malformed font data can be exploited to achieve remote code execution or system denial of service. The vulnerability specifically manifests when processing a crafted PFR1 chunk, which triggers unexpected behavior in the module's handling of signed and unsigned integer operations. The flaw exploits fundamental memory management principles where improper sign extension leads to invalid memory access patterns that can be leveraged by malicious actors to compromise system integrity.
The technical implementation of this vulnerability involves a sophisticated interplay between integer arithmetic and memory pointer management within Shockwave's font processing engine. When the Font Xtra.x32 module encounters a malformed PFR1 chunk, the unexpected sign extension causes a legitimate pointer to be interpreted as an invalid memory address. This results in an invalid pointer dereference that can be manipulated to overwrite critical memory locations or redirect program execution flow. The vulnerability operates at the intersection of multiple security domains including memory safety, integer overflow handling, and privilege escalation mechanisms. The flaw aligns with CWE-129, which addresses improper validation of array indices, and CWE-191, which covers integer underflow and overflow conditions. Additionally, the vulnerability demonstrates characteristics consistent with ATT&CK technique T1059.007 for process injection and T1203 for legitimate program execution, as exploitation requires the target system to execute malicious code within the Shockwave Player context.
The operational impact of CVE-2011-0556 extends beyond simple denial of service scenarios to encompass full system compromise capabilities for attackers with remote access. The vulnerability can be exploited through web-based attacks where users inadvertently visit malicious websites hosting compromised Shockwave content, making it particularly dangerous in enterprise environments where Shockwave Player remains in use. The memory corruption aspect of the flaw allows attackers to potentially execute arbitrary code with the privileges of the Shockwave Player process, which typically runs with user-level permissions but can provide a foothold for further exploitation. Organizations using outdated Shockwave Player versions face significant risk as this vulnerability has been actively exploited in the wild, particularly targeting systems where Shockwave remains enabled for legacy multimedia content delivery. The exploitability factor is enhanced by the fact that Shockwave Player was commonly enabled by default in many browsers and applications, creating a broad attack surface that extends beyond typical sandboxing boundaries.
Mitigation strategies for CVE-2011-0556 center on immediate patching and operational security measures to reduce exposure. Adobe released version 11.5.9.620 which addresses the vulnerability through proper bounds checking and sign extension handling in the Font Xtra.x32 module. Organizations should prioritize immediate deployment of this patch across all systems running affected Shockwave Player versions. Additional protective measures include disabling Shockwave Player functionality in web browsers where possible, implementing network-based filtering to block malicious PFR1 content, and monitoring for exploitation attempts through security information and event management systems. The vulnerability highlights the importance of maintaining current software versions and demonstrates why legacy multimedia plugins pose ongoing security risks. Security teams should also consider implementing application whitelisting policies that restrict execution of Shockwave Player unless absolutely necessary, as the plugin's continued use exposes systems to similar vulnerabilities. Regular security assessments should include evaluation of legacy multimedia components and their potential exploitation vectors, particularly in environments where older Shockwave content remains critical for business operations but requires careful security management to prevent exploitation.