CVE-2025-3407: Nothings Stb Image.h RCE Vulnerability

CVE-2025-3407 Overview

CVE-2025-3407 is an out-of-bounds read vulnerability in the Nothings stb library, specifically affecting the stbhw_build_tileset_from_image function in stb_herringbone_wang_tile.h. The flaw stems from improper validation of the h_count and v_count arguments, which control tileset dimensions parsed from input images. The library follows a rolling release model, and the affected commit is f056911. The vendor was contacted prior to disclosure but did not respond. Applications and games that embed stb for procedural tile generation inherit this defect when they accept untrusted image inputs.

Critical Impact

Attackers can trigger out-of-bounds memory reads by supplying a crafted image with malicious h_count or v_count values, leading to information disclosure or process crashes in applications embedding the affected stb module.

Affected Products

• Nothings stb (single-file header library collection)
• stb_herringbone_wang_tile.h at commit f056911 and prior rolling releases
• Downstream applications statically linking the vulnerable header

Discovery Timeline

• 2025-04-08 - CVE-2025-3407 published to NVD
• 2025-10-16 - Last updated in NVD database

Technical Details for CVE-2025-3407

Vulnerability Analysis

The vulnerability is classified under [CWE-119], improper restriction of operations within the bounds of a memory buffer. The stbhw_build_tileset_from_image function constructs a Wang tileset by iterating over a source image divided into h_count by v_count tiles. When these counts are not validated against the actual image dimensions, the function reads pixels outside the allocated image buffer.

Because stb is distributed as a header-only library and embedded directly into consumer applications, exploitation depends on whether the host application passes attacker-controlled values to the affected function. Many tools that use stb for asset processing accept tileset images from users, networks, or content pipelines.

The attack requires user interaction, such as opening a malicious tileset image, but does not require authentication or local access. The out-of-bounds read can leak adjacent heap memory or trigger an access violation that terminates the process.

Root Cause

The root cause is missing bounds validation on the h_count and v_count parameters before they are used to index into the image buffer. The function trusts caller-supplied tile counts and computes pixel offsets without verifying that the product of tile count and tile size remains within the image dimensions.

Attack Vector

The vulnerability is reachable over the network when an application using stb processes attacker-supplied tileset images. The attacker crafts an image with header metadata or parameter values that cause h_count or v_count to exceed valid ranges. When the host application invokes stbhw_build_tileset_from_image, the parser dereferences memory outside the image buffer.

No verified public proof-of-concept is available. Technical details are referenced in VulDB #303685.

Detection Methods for CVE-2025-3407

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications that process tileset or Wang tile images via stb
• Anomalous memory access violations originating from modules statically linked with stb_herringbone_wang_tile.h
• Malformed image files with implausible tile count fields received from untrusted sources

Detection Strategies

• Audit source trees and build artifacts for embedded copies of stb_herringbone_wang_tile.h at or before commit f056911
• Run fuzzing harnesses such as libFuzzer or AFL++ against stbhw_build_tileset_from_image with mutated h_count and v_count inputs
• Enable AddressSanitizer (ASan) in development and CI builds to surface out-of-bounds reads during testing

Monitoring Recommendations

• Monitor crash telemetry and Windows Error Reporting for repeated faults in image-processing components
• Log and inspect ingestion pipelines that accept user-supplied tileset images for parser exceptions
• Track upstream stb repository commits for an official patch addressing the bounds check

How to Mitigate CVE-2025-3407

Immediate Actions Required

• Inventory all internal projects and dependencies that vendor stb_herringbone_wang_tile.h and identify those exposing it to untrusted input
• Restrict the function to trusted, validated image sources until an upstream fix is published
• Add caller-side validation to ensure h_count and v_count are consistent with the image width and height before invoking the function

Patch Information

No official patch is available at the time of writing. The stb project uses rolling releases, and the vendor has not responded to disclosure. Maintainers consuming the library should monitor the Nothings stb repository for fix commits and rebuild dependent binaries when available.

Workarounds

• Reject tileset images whose declared tile counts do not divide evenly into image dimensions
• Sandbox image parsing in a separate, low-privilege process to contain potential information disclosure
• Apply a local patch enforcing h_count * tile_w <= image_w and v_count * tile_h <= image_h before any pixel access

# Configuration example: locate vulnerable stb usage in a codebase
grep -rn "stbhw_build_tileset_from_image" ./src
grep -rn "stb_herringbone_wang_tile.h" ./third_party