CVE-2021-21049 in Photoshop
Summary
by MITRE • 02/12/2021
Adobe Photoshop versions 21.2.4 (and earlier) and 22.1.1 (and earlier) are affected by an Out-of-bounds Read vulnerability when parsing a specially crafted file. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.
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Analysis
by VulDB Data Team • 02/28/2021
Adobe Photoshop versions 21.2.4 and earlier, as well as 22.1.1 and earlier, contain a critical out-of-bounds read vulnerability identified as CVE-2021-21049. This flaw exists within the file parsing functionality when processing specially crafted malicious files that exploit memory access violations. The vulnerability stems from insufficient bounds checking during the parsing of specific file formats, allowing an attacker to manipulate memory access patterns that extend beyond allocated buffer boundaries. The technical implementation of this vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a classic example of memory safety issues that enable arbitrary code execution. When a malicious file is opened by an unsuspecting user, the application's parsing routine attempts to read data beyond the intended memory limits, creating opportunities for attackers to inject and execute arbitrary code with the privileges of the current user context.
The operational impact of this vulnerability is significant as it requires only user interaction to exploit, making it particularly dangerous in targeted attack scenarios. An unauthenticated attacker can craft malicious files designed to trigger the out-of-bounds read condition when opened by a victim using vulnerable Photoshop versions. This attack vector leverages the principle of least privilege by executing code within the application's trusted execution environment, potentially allowing for privilege escalation or data exfiltration. The vulnerability's exploitation path follows ATT&CK technique T1059.007 for command and script interpreter usage, as successful exploitation could enable attackers to execute arbitrary commands through the compromised Photoshop process. The attack surface is broadened by the widespread adoption of Photoshop in creative workflows, making it an attractive target for adversaries seeking persistent access to creative agencies, design firms, or individual users who regularly handle image files from untrusted sources.
Mitigation strategies for CVE-2021-21049 should prioritize immediate patch management with Adobe's security updates, as the vulnerability affects multiple product versions across different release cycles. Organizations should implement strict file validation procedures, including sandboxing of image file processing and content filtering for suspicious file types. Network-level defenses can include email filtering systems that scan for potentially malicious image files and implement sandboxing solutions for file analysis before user access. Security teams should monitor for indicators of compromise related to this vulnerability, particularly unusual file access patterns or execution of unexpected processes. The recommended defense-in-depth approach includes user education on avoiding suspicious file attachments, implementing application whitelisting policies to restrict Photoshop usage, and maintaining regular backup procedures to recover from potential exploitation. Additionally, system administrators should consider disabling unnecessary file format support within Photoshop to reduce the attack surface, while network segmentation can limit the potential lateral movement if exploitation occurs. Continuous monitoring and vulnerability assessment programs should track similar memory safety issues in creative software suites to prevent similar future incidents, as this vulnerability demonstrates the ongoing challenges in ensuring memory safety within complex multimedia applications.