CVE-2025-43967: Struktur Libheif Use-After-Free Vulnerability

CVE-2025-43967 Overview

CVE-2025-43967 is a NULL pointer dereference vulnerability discovered in libheif, an open-source library for reading and writing HEIF and AVIF image files. The vulnerability exists in the ImageItem_Grid::get_decoder function within image-items/grid.cc, where a specially crafted grid image can reference a nonexistent image item, leading to a denial of service condition.

Critical Impact

This vulnerability can be exploited remotely without authentication to cause application crashes, resulting in denial of service for applications that process untrusted HEIF/AVIF images using vulnerable versions of libheif.

Affected Products

• struktur libheif versions prior to 1.19.6
• Applications and services using vulnerable libheif versions for image processing
• Image viewers, converters, and web services that handle HEIF/AVIF files

Discovery Timeline

• 2025-04-21 - CVE-2025-43967 published to NVD
• 2025-05-08 - Last updated in NVD database

Technical Details for CVE-2025-43967

Vulnerability Analysis

This vulnerability represents a NULL pointer dereference condition (CWE-476) that occurs during grid image processing in libheif. When the library attempts to decode a grid image, it calls the get_decoder function to retrieve the decoder for referenced image items. However, if a malicious HEIF file contains a grid image that references an image item ID that does not exist in the file's item collection, the code fails to validate the reference before attempting to use it.

The attack can be initiated remotely through network-accessible services that process user-supplied images. No privileges or user interaction are required, making this vulnerability particularly dangerous for web services and automated image processing pipelines. While the vulnerability does not enable data exfiltration or arbitrary code execution, it can cause complete service disruption through application crashes.

Root Cause

The root cause lies in insufficient input validation when processing grid image references. The ImageItem_Grid::get_decoder function did not verify that referenced image item IDs actually exist in the m_all_images collection before attempting to access them. When an invalid reference is encountered, the code attempts to dereference a NULL or invalid pointer, resulting in a crash.

Attack Vector

An attacker can exploit this vulnerability by crafting a malicious HEIF or AVIF image file containing a grid image structure with references to nonexistent image item IDs. When a vulnerable application attempts to decode this file, the library crashes due to the NULL pointer dereference. This attack vector is particularly effective against:

• Web applications that allow image uploads
• Image conversion services
• Content management systems processing user media
• Messaging applications that preview images

// Security patch in libheif/context.cc - detect when image references non-existing item (#1455)
     }
   }
   else {
+    if (m_all_images.find(id) == m_all_images.end()) {
+      std::stringstream sstr;
+      sstr << "Image item " << id << " referenced, but it does not exist\n";
+
+      return Error(heif_error_Invalid_input,
+        heif_suberror_Nonexisting_item_referenced,
+        sstr.str());
+    }
+    else if (dynamic_cast<ImageItem_Error*>(m_all_images.find(id)->second.get())) {
+      // Should er return an error here or leave it to the follow-up code to detect that?
+    }
+
     out = id;
     return Error::Ok;
   }

Source: GitHub Commit 6e35af7

Detection Methods for CVE-2025-43967

Indicators of Compromise

• Unexpected application crashes when processing HEIF or AVIF image files
• Segmentation fault errors in logs referencing libheif or grid image processing
• Service restarts coinciding with image upload or processing operations
• Core dumps or crash reports indicating NULL pointer access in grid.cc or related libheif components

Detection Strategies

• Monitor application logs for segmentation faults and NULL pointer dereference errors associated with image processing operations
• Implement file integrity monitoring to detect unusual patterns in uploaded HEIF/AVIF files
• Deploy runtime application self-protection (RASP) to detect and block exploitation attempts
• Use SentinelOne Singularity to detect anomalous process crashes and potential exploitation patterns

Monitoring Recommendations

• Configure alerting for repeated crashes in services that process image files
• Track libheif version deployments across your infrastructure using software composition analysis
• Implement logging at the application layer to capture metadata about processed images before crashes
• Set up automated vulnerability scanning to identify systems running vulnerable libheif versions

How to Mitigate CVE-2025-43967

Immediate Actions Required

• Upgrade libheif to version 1.19.6 or later immediately on all affected systems
• Audit applications and services for libheif dependencies, including transitive dependencies
• Consider temporarily disabling HEIF/AVIF processing capabilities for untrusted inputs until patching is complete
• Implement input validation at the application layer to reject malformed image files before they reach libheif

Patch Information

The vulnerability has been addressed in libheif version 1.19.6. The fix adds proper validation to check whether referenced image item IDs exist in the m_all_images collection before attempting to access them. If a nonexistent reference is detected, the library now returns a descriptive error (heif_error_Invalid_input with heif_suberror_Nonexisting_item_referenced) instead of crashing.

For detailed information about the security patch, refer to the GitHub commit 6e35af7 and the version comparison between v1.19.5 and v1.19.6. Additional context is available in GitHub Issue #1455.

Workarounds

• Implement strict file type validation at the application boundary to limit accepted image formats
• Deploy web application firewalls (WAF) with rules to inspect and reject potentially malicious HEIF files
• Isolate image processing operations in sandboxed environments to contain crash impacts
• Use process supervision to automatically restart crashed services while maintaining availability

# Check installed libheif version
pkg-config --modversion libheif

# Update libheif on Debian/Ubuntu systems
sudo apt update && sudo apt install libheif1

# Verify updated version
pkg-config --modversion libheif
# Expected output: 1.19.6 or higher