CVE-2020-6116 in Nitro Pro
Summary
by MITRE
An arbitrary code execution vulnerability exists in the rendering functionality of Nitro Software, Inc.’s Nitro Pro 13.13.2.242. When drawing the contents of a page using colors from an indexed colorspace, the application can miscalculate the size of a buffer when allocating space for its colors. When using this allocated buffer, the application can write outside its bounds and cause memory corruption which can lead to code execution. A specially crafted document must be loaded by a victim in order to trigger this vulnerability.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/18/2020
The vulnerability identified as CVE-2020-6116 represents a critical buffer overflow condition within Nitro Pro 13.13.2.242, specifically affecting the application's PDF rendering engine. This flaw resides in the handling of indexed colorspaces during page content rendering, where the software fails to properly calculate buffer sizes when allocating memory for color data. The issue manifests when processing PDF documents containing indexed color information, creating a scenario where memory corruption occurs during the rendering process. According to CWE-121, this vulnerability falls under the category of stack-based buffer overflow, while the ATT&CK framework would classify this as a code execution primitive through memory corruption techniques. The vulnerability's exploitation requires a victim to open a specially crafted malicious document, making it a classic client-side attack vector that leverages social engineering to deliver the payload.
The technical implementation of this flaw involves the application's failure to validate color data boundaries when processing indexed colorspaces in PDF documents. When Nitro Pro encounters a page with indexed colors, it calculates buffer space based on incorrect assumptions about color data size, leading to insufficient memory allocation. During subsequent memory operations, the application writes beyond the allocated buffer boundaries, potentially overwriting adjacent memory regions including function pointers, return addresses, or other critical program data. This memory corruption can be systematically exploited to redirect program execution flow, allowing attackers to execute arbitrary code with the privileges of the victim user. The vulnerability demonstrates a classic memory safety issue where insufficient input validation and boundary checking create exploitable conditions.
The operational impact of CVE-2020-6116 extends beyond simple code execution, potentially enabling full system compromise when combined with other attack techniques. Attackers can craft malicious PDF documents that, when opened by an unsuspecting user, automatically trigger the buffer overflow condition. This vulnerability affects organizations using Nitro Pro for document processing, particularly those handling untrusted PDF content from external sources. The exploitability factor is moderate to high since it requires user interaction but can lead to complete system compromise. Organizations may experience unauthorized data access, privilege escalation, or persistent backdoor installation. Security professionals should consider this vulnerability in their risk assessment frameworks, particularly when evaluating document processing applications and their exposure to untrusted content from the internet or external parties.
Mitigation strategies for CVE-2020-6116 should encompass both immediate defensive measures and long-term architectural improvements. Organizations should prioritize patching Nitro Pro installations to versions that address the buffer overflow condition, as provided by Nitro Software Inc. Implementing strict document validation policies, including sandboxed PDF processing environments, can significantly reduce exploitation risks. Network-level defenses such as web application firewalls and content filtering systems should be configured to block suspicious PDF content from untrusted sources. Additionally, user education programs should emphasize the dangers of opening unverified documents, particularly those received via email or downloaded from unknown websites. Security monitoring should include detection of unusual PDF processing activities and memory access patterns that may indicate exploitation attempts. The vulnerability highlights the importance of memory safety in document rendering engines and reinforces the need for regular security assessments of third-party software components.