CVE-2024-27929 Overview
CVE-2024-27929 is a heap use-after-free vulnerability [CWE-416] in SixLabors ImageSharp, a managed cross-platform 2D graphics library for .NET. The flaw resides in the InitializeImage() function within PngDecoderCore.cs. An attacker triggers the vulnerability by supplying a specially crafted PNG image to ImageSharp for conversion. Successful exploitation can lead to information disclosure or process crashes. The maintainers patched the issue in versions 3.1.3 and 2.1.7.
Critical Impact
A malicious PNG file processed by ImageSharp can trigger heap memory corruption in the PNG decoder, exposing sensitive process memory or causing denial of service in applications that accept untrusted image input.
Affected Products
- SixLabors ImageSharp versions prior to 2.1.7 (2.x branch)
- SixLabors ImageSharp versions prior to 3.1.3 (3.x branch)
- .NET applications that decode untrusted PNG files with vulnerable ImageSharp releases
Discovery Timeline
- 2024-03-05 - CVE-2024-27929 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-27929
Vulnerability Analysis
The vulnerability is a heap use-after-free condition [CWE-416] in ImageSharp's PNG decoder. When InitializeImage() in PngDecoderCore.cs processes a crafted PNG file, the decoder references heap memory that has already been freed. Subsequent reads or writes to that dangling reference lead to undefined behavior. In managed .NET code, this class of flaw commonly stems from mishandled buffers rented from pooled allocators or improper disposal of pixel-buffer resources. The observed impact includes leakage of adjacent heap contents and application termination.
Root Cause
The root cause is improper lifetime management of a heap-allocated buffer used during PNG image initialization. The decoder retains a reference to memory that has been released back to the allocator, then accesses it while decoding attacker-controlled PNG chunks. Chunk ordering and header parameters supplied by the attacker influence which freed region is reused, controlling what data is read.
Attack Vector
Exploitation requires an attacker to deliver a malicious PNG file to an application that calls ImageSharp to decode or convert the image. User interaction is required (UI:R), and the attack vector is local (AV:L) in the CVSS metric, reflecting scenarios where a user opens or uploads the file for local processing. Web applications that accept PNG uploads and process them server-side with ImageSharp are exposed when the upload path treats the parsed image as untrusted input.
No public proof-of-concept code is currently listed for this issue. Refer to the SixLabors GitHub Security Advisory GHSA-65x7-c272-7g7r for maintainer-provided technical detail.
Detection Methods for CVE-2024-27929
Indicators of Compromise
- Unexpected crashes, AccessViolationException, or heap corruption faults in .NET processes that invoke ImageSharp decoders.
- PNG files with malformed or unusual chunk sequences (for example, oversized or truncated IHDR, IDAT, or ancillary chunks) submitted to upload endpoints.
- Application logs showing repeated failures inside PngDecoderCore or during image conversion operations.
Detection Strategies
- Inventory .NET application dependencies and flag any use of SixLabors.ImageSharp at versions below 2.1.7 or 3.1.3 via SBOM analysis or dotnet list package --vulnerable.
- Enable structured exception and crash telemetry for image-processing services and alert on faults originating from ImageSharp assemblies.
- Deploy file-content inspection at ingress points to sanity-check PNG headers and chunk structures before handing them to the decoder.
Monitoring Recommendations
- Monitor process stability and memory metrics for services that decode user-supplied images; sudden restarts or worker recycles can indicate exploitation attempts.
- Correlate upload activity with subsequent application errors to identify sources of malicious PNG submissions.
- Track outbound traffic from image-processing workloads to detect potential data exfiltration following an information-disclosure event.
How to Mitigate CVE-2024-27929
Immediate Actions Required
- Upgrade SixLabors.ImageSharp to version 3.1.3 on the 3.x branch or 2.1.7 on the 2.x branch across all projects.
- Rebuild and redeploy any application, container image, or serverless function that bundles a vulnerable ImageSharp assembly.
- Audit third-party libraries that transitively depend on ImageSharp and verify they pull a patched version.
Patch Information
The maintainers released fixed versions 2.1.7 and 3.1.3. Both patches address the heap use-after-free in InitializeImage() within PngDecoderCore.cs. Details are published in the SixLabors GitHub Security Advisory GHSA-65x7-c272-7g7r.
Workarounds
- Reject or quarantine PNG uploads at the edge until the patched ImageSharp version is deployed.
- Validate PNG file structure with a separate lightweight parser before invoking ImageSharp for decoding.
- Run image-processing workloads in isolated, low-privilege sandboxes so that a successful information-disclosure exploit yields minimal sensitive data.
# Update SixLabors.ImageSharp to a patched version
dotnet add package SixLabors.ImageSharp --version 3.1.3
# For projects pinned to the 2.x branch
dotnet add package SixLabors.ImageSharp --version 2.1.7
# Verify no vulnerable versions remain
dotnet list package --vulnerable --include-transitive
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
