CVE-2025-62821: Microsoft HEIF Buffer Overflow Flaw

CVE-2025-62821 Overview

CVE-2025-62821 is an out-of-bounds read vulnerability in Microsoft HEIF Image Extensions version 1.2.22.0. The flaw resides in the CHEIFItemInfoEntry_GetDataSize function, which can return success while leaving the reported data size as 0. A caller then performs a 1-byte allocation, after which CopyPixels computes copy_size = stride * abs(roi_height) and invokes memmove without validating the source buffer length. Processing a malformed HEIF image is sufficient to trigger memory disclosure. The vulnerability is classified under [CWE-125: Out-of-Bounds Read].

Critical Impact
Remote attackers can trigger an out-of-bounds read leading to confidentiality compromise and process crashes when a user opens a crafted HEIF file.

Affected Products

Microsoft HEIF Image Extensions 1.2.22.0
Windows systems with the HEIF Image Extensions component installed
Applications relying on the Windows Imaging Component for HEIF decoding

Discovery Timeline

2026-06-19 - CVE-2025-62821 published to NVD
2026-06-22 - Last updated in NVD database

Technical Details for CVE-2025-62821

Vulnerability Analysis

The vulnerability resides in how the HEIF Image Extensions library handles item information entries during image decoding. The function CHEIFItemInfoEntry_GetDataSize returns a success status code even when the parsed data size equals 0. Callers interpret the success return as a signal to allocate buffer space proportional to the reported size, resulting in a 1-byte allocation when the size is zero.

Later in the decoding pipeline, CopyPixels calculates a copy size using stride * abs(roi_height). The function then issues a memmove operation against the undersized source buffer. Because the source length is never compared against the computed copy size, the memmove reads memory well beyond the allocated 1-byte region, exposing adjacent heap contents.

The attack vector is network-accessible because HEIF files can be delivered through email attachments, web downloads, messaging applications, or any service that previews image content using Windows imaging APIs. Exploitation requires no privileges and no user interaction beyond standard image preview behavior.

Root Cause

The root cause is missing validation between two parsing stages. CHEIFItemInfoEntry_GetDataSize conflates the absence of data with a successful parse, and CopyPixels trusts the resulting buffer without re-checking its length before performing bulk memory operations. The result is an unchecked read past the end of a 1-byte allocation.

Attack Vector

An attacker crafts a HEIF image where the item information entry produces a zero data size while the region-of-interest dimensions remain non-zero. When a target opens or previews the file through any application that loads the HEIF Image Extensions, the out-of-bounds read executes. A public proof-of-concept is hosted at the GitHub PoC Repository.

Detection Methods for CVE-2025-62821

Indicators of Compromise

HEIF or HEIC files with malformed item information entries where the reported data size is 0 but ROI dimensions are non-zero
Application crashes or access violations in processes loading heif.dll or related Windows Imaging Component modules
Unexpected memory faults in explorer.exe, Photos.exe, or other image-handling processes after opening HEIF content

Detection Strategies

Inspect HEIF file headers and item information boxes for inconsistencies between declared data size and pixel dimensions
Monitor Windows Error Reporting events tied to image preview handlers for repeated faults referencing HEIF decoder modules
Apply YARA rules targeting HEIF structures with zero-length iloc extents combined with non-zero ispe properties

Monitoring Recommendations

Log image file downloads and email attachments with .heif and .heic extensions for retrospective analysis
Alert on crashes in processes that load HEIF Image Extensions, particularly when triggered by externally sourced files
Track installed versions of Microsoft HEIF Image Extensions across the fleet to identify unpatched endpoints

How to Mitigate CVE-2025-62821

Immediate Actions Required

Inventory all Windows endpoints with Microsoft HEIF Image Extensions 1.2.22.0 installed via the Microsoft Store
Update the HEIF Image Extensions package through the Microsoft Store to the latest available version
Restrict opening HEIF files from untrusted sources until patching is verified

Patch Information

Microsoft distributes HEIF Image Extensions through the Microsoft Store. Administrators should ensure Store apps receive updates and confirm the installed version is later than 1.2.22.0. Monitor the Microsoft Security Response Center for the official advisory matching CVE-2025-62821.

Workarounds

Uninstall Microsoft HEIF Image Extensions from systems that do not require HEIF rendering
Block HEIF and HEIC attachments at the email gateway and web proxy until patches are deployed
Disable image preview in file explorer and email clients for user populations at elevated risk

bash

# Configuration example - check installed HEIF Image Extensions version
Get-AppxPackage -Name Microsoft.HEIFImageExtension | Select-Object Name, Version

# Remove the extension if not required
Get-AppxPackage -Name Microsoft.HEIFImageExtension | Remove-AppxPackage