CVE-2026-120432 in Netpbm
Summary
by MITRE • 11/02/2026
Netpbm before 10.86.51, 11.02.30, and 11.15.08 contains an integer overflow vulnerability in winicontopam that allows attackers to corrupt heap memory via oversized ICO/CUR dimensions. Attackers can supply a crafted icon file with width or height above 32767, wrapping int16_t loop counters into negative row buffer indices to cause crashes or potential code execution.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified in Netpbm versions prior to 10.86.51, 11.02.30, and 11.15.08 represents a critical security flaw within the winicontopam utility component of the suite. This specific tool is designed to convert Windows icon files into PAM format images for further processing by other Netpbm utilities. The core issue stems from an integer overflow condition that occurs during the parsing and handling of image dimensions, specifically affecting the width and height attributes embedded within ICO or CUR file headers. Because these dimension values are processed using signed 16-bit integers (int16_t), they have a maximum positive value limit of 32767. When an attacker supplies a crafted icon file with either the width or height exceeding this threshold, the integer representation wraps around to become negative due to two's complement arithmetic rules inherent in C programming languages and most modern computing architectures.
This mathematical wrapping leads directly to heap memory corruption because subsequent operations rely on these dimension values to allocate buffers and iterate through pixel data rows. Specifically, loop counters initialized with the wrapped negative dimensions result in invalid array indexing when accessing row buffers allocated based on expected positive sizes. Instead of triggering a bounds check failure or allocating insufficient memory safely, the application proceeds to write data at memory addresses calculated from these negative indices. This behavior effectively allows an attacker to perform out-of-bounds writes into adjacent heap structures, corrupting metadata such as allocation headers or pointers stored nearby in memory. Such corruption destabilizes the program's internal state and creates a primitive that can be leveraged for more severe exploits.
The operational impact of this vulnerability is significant, ranging from denial of service to arbitrary code execution depending on the context in which Netpbm operates. In typical usage scenarios where users process untrusted image files, an attacker could craft a malicious ICO file containing oversized dimensions to trigger immediate crashes via segmentation faults or access violations caused by invalid memory writes. However, given that heap corruption is involved, sophisticated attackers can manipulate the corrupted data structures to overwrite function pointers or return addresses on the stack. This technique enables remote code execution with the privileges of the user running the Netpbm utility. If the software is deployed in a server environment processing uploaded images automatically, this vulnerability becomes remotely exploitable over network services that accept image uploads without rigorous validation.
From a classification perspective, this flaw aligns closely with CWE-190 Integer Overflow or Wraparound and CWE-787 Out-of-bounds Write. The exploitation path typically maps to MITRE ATT&CK techniques involving memory corruption for privilege escalation or code injection, specifically falling under the category of invalid memory access leading to arbitrary write capabilities. Defense-in-depth strategies are essential here since input validation alone may not suffice if multiple parsing libraries are involved in a pipeline. Mitigation requires immediate upgrading to patched versions where dimension checks enforce strict upper bounds before allocation and iteration logic begins. Additionally, implementing sandboxing for image processing services can limit the blast radius of any successful exploitation attempt by restricting file system access and network connectivity for processes handling untrusted media files.