CVE-2026-120431 in Netpbm
Summary
by MITRE • 11/02/2026
Netpbm before 10.86.51, 11.x before 11.02.29, and 11.03 before 11.15.07 contains a heap-based buffer overflow in sgitopnm's readChannels() function when processing RLE-compressed SGI images. Attackers can supply crafted SGI files with oversized offset table lengths to write controlled data past the heap buffer, causing 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.x before 11.02.29, and 11.03 before 11.15.07 represents a critical heap-based buffer overflow within the sgitopnm utility. This specific component is responsible for converting Silicon Graphics Image files into other Netpbm formats. The root cause of this flaw lies in the readChannels function, which handles the parsing and processing of Run-Length Encoded RLE compressed SGI images. During the initialization phase of reading these image channels, the software fails to adequately validate the length values found within the offset table embedded in the file header or metadata structure. This lack of rigorous bounds checking allows an attacker who supplies a specially crafted SGI file with oversized offset table lengths to trigger a memory corruption event.
From a technical perspective, when the readChannels function processes these malformed inputs, it allocates heap memory based on potentially untrusted size parameters derived from the input file without verifying that they fall within expected or safe limits. Consequently, subsequent write operations attempt to place data into this buffer beyond its allocated boundaries. This results in writing controlled data past the end of the heap buffer, corrupting adjacent memory structures such as metadata pointers, allocation headers, or other objects residing on the heap. The immediate operational impact of this corruption is often a program crash due to segmentation faults or access violations when the corrupted memory is accessed later during execution. However, the severity escalates significantly because modern operating systems and compilers employ various mitigations that can sometimes be bypassed through precise exploitation techniques.
The potential for arbitrary code execution exists if an attacker can carefully craft the overflow payload to overwrite function pointers, exception handlers, or other control flow data on the heap with shellcode or return-oriented programming gadgets. This aligns closely with CWE-122 Heap-based Buffer Overflow, which describes writing beyond the bounds of a buffer allocated on the heap. The exploitation vector is classified under CWE-20 Improper Input Validation, as the application fails to verify that user-supplied input conforms to expected constraints before processing it. In terms of attack tactics, this vulnerability facilitates initial access and potentially privilege escalation depending on the context in which sgitopnm runs, mapping to MITRE ATT&CK techniques related to memory corruption exploitation such as T1203 Exploitation for Client Execution if triggered via a client application or service that processes untrusted images.
To mitigate this risk, organizations relying on Netpbm must immediately upgrade to version 10.86.51 or later, specifically ensuring the use of 11.02.29+ for the 11.x branch and 11.15.07+ for the 11.03 branch where these fixes are integrated. Until an upgrade is feasible, it is advisable to restrict access to any services or applications that utilize sgitopnm with untrusted input sources. Implementing strict file type validation at the network perimeter and employing sandboxed environments for processing image files can further reduce the attack surface. Additionally, enabling heap protection mechanisms such as Address Space Layout Randomization ASLR and Data Execution Prevention DEP on target systems may hinder exploitation attempts by making it more difficult to predict memory layouts or execute injected code directly from the heap.