CVE-2024-6821 Overview
CVE-2024-6821 is an out-of-bounds write vulnerability [CWE-787] in IrfanView's CIN file parser. The flaw allows attackers to execute arbitrary code in the context of the current user when a victim opens a crafted .CIN image file. IrfanView is a widely deployed Windows image viewer, expanding the potential attack surface across desktop environments.
The vulnerability was reported through the Trend Micro Zero Day Initiative as ZDI-CAN-23260 and published in the Zero Day Initiative Advisory ZDI-24-973. IrfanView 4.66 (x64) is confirmed affected.
Critical Impact
Successful exploitation grants arbitrary code execution with the privileges of the user running IrfanView, enabling malware installation, credential theft, or lateral movement.
Affected Products
- IrfanView 4.66 (x64)
- IrfanView installations that process Kodak Cineon (.CIN) image files
- Windows endpoints with IrfanView configured as a default image handler
Discovery Timeline
- 2024-11-22 - CVE-2024-6821 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-6821
Vulnerability Analysis
The vulnerability resides in IrfanView's CIN file parsing logic. CIN (Kodak Cineon) is a raster image format commonly used in digital film production. When IrfanView opens a specially crafted CIN file, the parser fails to validate size fields before writing pixel or metadata content into an allocated buffer.
This mismatch between declared and actual data lengths produces an out-of-bounds write past the end of the buffer. Attackers can shape adjacent heap or stack memory to overwrite function pointers, return addresses, or object metadata, redirecting execution to attacker-controlled code.
Root Cause
The root cause is missing validation of user-supplied length or dimension fields inside the CIN header before performing buffer writes. IrfanView trusts values embedded in the file and allocates or indexes buffers without cross-checking against the actual file size or fixed bounds, resulting in a classic CWE-787 condition.
Attack Vector
Exploitation requires user interaction. An attacker delivers a malicious .CIN file through email, a web download, or a shared drive, then convinces the victim to open it in IrfanView. Local file opening is sufficient; no network service is exposed. The scope remains within the process context, so code executes with the current user's privileges.
The vulnerability mechanism is described in prose only, as no verified public exploit code is available. See the Zero Day Initiative Advisory ZDI-24-973 for technical details.
Detection Methods for CVE-2024-6821
Indicators of Compromise
- Unexpected child processes spawned by i_view64.exe or i_view32.exe, such as cmd.exe, powershell.exe, or rundll32.exe
- IrfanView process crashes with access violation exceptions when opening .CIN files
- .CIN files arriving through email attachments, downloads, or removable media on systems that do not use Cineon workflows
- Outbound network connections initiated by the IrfanView process shortly after opening an image
Detection Strategies
- Monitor process creation events where the parent image is IrfanView and the child is a scripting, shell, or LOLBin binary
- Alert on Windows Error Reporting or crash dumps involving i_view*.exe correlated with recent .CIN file access
- Apply YARA rules against inbound files targeting anomalous CIN header fields, such as oversized image dimensions
Monitoring Recommendations
- Enable command-line and process-tree logging on endpoints running IrfanView
- Track file-write and file-open telemetry for .CIN extensions across user profiles and download directories
- Correlate IrfanView execution events with subsequent unusual memory allocations or module loads
How to Mitigate CVE-2024-6821
Immediate Actions Required
- Inventory all endpoints running IrfanView 4.66 or earlier and prioritize upgrades
- Update IrfanView to the latest version that addresses the CIN parser issue as published by the vendor
- Restrict opening of untrusted .CIN files, especially from email attachments or external sources
- Enforce least-privilege user accounts so exploitation does not yield administrative access
Patch Information
Refer to the Zero Day Initiative Advisory ZDI-24-973 and the official IrfanView downloads page for the fixed release. No vendor advisory URL is included in the NVD record at the time of publication. Administrators should validate the installed version through the IrfanView Help > About menu or by checking the i_view64.exe file version metadata.
Workarounds
- Remove .CIN file associations from IrfanView until patching is complete
- Block delivery of .CIN attachments at email and web gateways where the format is not required
- Apply Windows Defender Exploit Guard or equivalent Attack Surface Reduction rules to block child-process creation from image viewers
- Deploy application allowlisting to prevent unauthorized child processes launched from IrfanView
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
