Description

A flaw was found in the file-xwd plugin in GIMP. When processing a specially crafted XWD image file, the plugin validates the image width and bytes-per-line parameters independently rather than ensuring their combined values are consistent with the allocated buffer size. This incorrect validation leads to improper bounds checking, causing a heap out-of-bounds read. This issue can result in an application crash, leading to a denial of service, or a limited information disclosure of heap memory contents into the produced image.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.4",
  "pubDate": "2026-08-25T21:18:24.023Z",
  "pubdate": "2026-08-25T21:18:24.023Z",
  "executiveSummary": "A heap-based out-of-bounds read vulnerability has been identified in the GIMP file-xwd plugin. The flaw resides in the improper validation of XWD image parameters, specifically failing to enforce consistency between image width and bytes-per-line values relative to the allocated buffer size.\nThis vulnerability allows a remote attacker to trigger an application crash, resulting in a Denial of Service (DoS), or potentially leak sensitive information stored in heap memory. By crafting a malicious XWD file, an attacker can manipulate the plugin's parsing logic to read memory segments outside the intended buffer boundaries.\nThe vulnerability affects systems processing untrusted XWD images using GIMP. Successful exploitation requires the application to load a maliciously crafted file, typically initiated by a user. The risk is primarily associated with memory corruption and data leakage, which could expose sensitive information residing in the heap, such as credentials, cryptographic keys, or user data, which might then be embedded into the resulting output image.",
  "technicalDetails": "The vulnerability originates within the file-xwd plugin of GIMP, which is responsible for parsing and rendering XWD (X Window Dump) image files. The root cause is a logic error in the validation routines governing the processing of image metadata headers. Specifically, the plugin performs independent validation of the 'image width' and 'bytes-per-line' attributes without verifying that the product of these dimensions remains within the bounds of the pre-allocated heap memory buffer.\nDuring the image parsing process, the plugin allocates a heap buffer intended to store pixel data. Because the plugin does not implement strict bounds checking for the relationship between the bytes-per-line and the actual width, an attacker can manipulate the XWD header fields. By defining a bytes-per-line value that exceeds the intended width but remains within the bounds of the total allocated memory, the parser attempts to access memory regions beyond the scope of the current image row.\nThe exploitation flow proceeds as follows: First, the attacker creates a malformed XWD file with carefully engineered metadata values for width and row-stride. When GIMP attempts to open or process this file, the file-xwd plugin calculates an offset based on these manipulated parameters. Due to the lack of combined validation, the read operation proceeds to access adjacent heap memory. If the calculated offset points to an unmapped memory region, the application triggers a segmentation fault or memory access violation, resulting in an immediate crash (Denial of Service).\nIf the out-of-bounds offset maps to valid, adjacent heap memory, the plugin may read that arbitrary memory and incorporate the data into the image being constructed. Consequently, when the user views the resulting image, the contents of the adjacent heap memory—which may contain sensitive data—are rendered as pixel information. This results in an information disclosure vulnerability. The vulnerability does not require authentication or specific system privileges to initiate; it is triggered entirely through the interaction between the software and the attacker-provided input file. The exploit is effective provided the targeted system uses a version of GIMP containing the vulnerable file-xwd plugin implementation."
}