CVE-2020-6112 in Nitro Pro
Summary
by MITRE
An exploitable code execution vulnerability exists in the JPEG2000 Stripe Decoding functionality of Nitro Software, Inc.’s Nitro Pro 13.13.2.242 when decoding sub-samples. While initializing tiles with sub-sample data, the application can miscalculate a pointer for the stripes in the tile which allow for the decoder to write out of-bounds and cause memory corruption. This can result in code execution. A specially crafted image can be embedded inside a PDF and loaded by a victim in order to trigger this vulnerability.
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability described in CVE-2020-6112 represents a critical code execution flaw within Nitro Pro's JPEG2000 decoding implementation that demonstrates the inherent risks associated with complex multimedia processing libraries. This issue specifically affects Nitro Software's professional PDF editing and viewing application, where the vulnerability manifests during the decoding of JPEG2000 format images, particularly when handling sub-sampled data within image stripes. The flaw exists in the tile initialization process where pointer calculations become miscalculated, creating conditions that allow for out-of-bounds memory writes that can be exploited to achieve arbitrary code execution.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and more specifically with CWE-787, representing out-of-bounds write vulnerabilities. The flaw occurs when the application processes JPEG2000 images embedded within PDF documents, where Nitro Pro attempts to decode sub-sampled data for tile rendering. During this process, the decoder incorrectly calculates memory pointers for stripe data structures, leading to memory corruption when the application attempts to write data beyond the allocated memory boundaries. This pointer miscalculation creates a predictable pattern that attackers can exploit to overwrite critical memory locations, potentially including return addresses or function pointers, thereby enabling remote code execution.
The operational impact of this vulnerability extends beyond simple local exploitation scenarios, as it can be triggered through legitimate document processing activities that are common in enterprise environments. Attackers can craft malicious JPEG2000 images that, when embedded within PDF documents, will automatically trigger the vulnerable code path when victims open these documents in Nitro Pro. This makes the vulnerability particularly dangerous in phishing campaigns or targeted attacks where adversaries can leverage the application's legitimate document processing capabilities to deliver payloads. The attack vector through PDF documents aligns with ATT&CK technique T1204.002, which describes legitimate user execution through exploitation of document processing applications, making this vulnerability particularly effective for social engineering campaigns.
Mitigation strategies for CVE-2020-6112 should focus on immediate patching of affected Nitro Pro versions, as the vulnerability affects specifically version 13.13.2.242 and potentially other versions within the same release cycle. Organizations should implement network-based restrictions to prevent the automatic loading of potentially malicious PDF documents, particularly those containing embedded JPEG2000 images. Additionally, security measures should include application whitelisting to prevent execution of untrusted binaries, memory protection mechanisms such as DEP and ASLR, and regular security updates to address similar vulnerabilities in multimedia processing libraries. The vulnerability demonstrates the importance of input validation and bounds checking in multimedia decoders, particularly those handling complex compression formats like JPEG2000 that involve sophisticated data structures and memory management operations.