CVE-2026-59204 in Pillow
Summary
by MITRE • 07/14/2026
Pillow is a Python imaging library. From 8.2.0 through 12.2.0, src/libImaging/Jpeg2KDecode.c accumulates total_component_width across every tile in a JPEG2000 image instead of recomputing it per tile, allowing a crafted tiled JPEG2000 file to force substantially higher transient memory usage and trigger out-of-memory failures during decoding. This issue is fixed in version 12.3.0.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability resides within the Pillow imaging library's handling of JPEG2000 image decoding, specifically in the Jpeg2KDecode.c source file where a critical memory management flaw exists between versions 8.2.0 and 12.2.0. This issue stems from improper accumulation of the total_component_width variable across all tiles within a tiled JPEG2000 image structure rather than recalculating this value for each individual tile. The flaw creates a condition where maliciously crafted JPEG2000 files can cause the decoder to allocate excessive memory resources during the decoding process, leading to significant transient memory consumption that can ultimately result in out-of-memory failures and system instability.
The technical implementation of this vulnerability demonstrates a classic memory corruption pattern where cumulative calculations bypass proper bounds checking mechanisms. When processing tiled JPEG2000 images, the decoder maintains a running total of component widths across all tiles without resetting or properly validating these accumulations per tile boundary. This accumulation behavior creates an exploitable condition where an attacker can craft a file containing numerous tiles with progressively increasing width values, causing the memory allocation to grow exponentially beyond normal expectations. The flaw aligns with CWE-129, which addresses improper handling of buffer boundaries, and reflects patterns commonly associated with memory exhaustion attacks.
The operational impact of this vulnerability extends beyond simple denial-of-service scenarios, creating potential security risks in environments where Pillow is used for image processing in untrusted contexts. Systems utilizing affected versions of Pillow become susceptible to memory exhaustion attacks that can be triggered through simple file uploads or network-based image processing operations. This vulnerability affects applications across multiple domains including web applications, content management systems, and any software that processes user-provided JPEG2000 images without proper input validation. The transient nature of the memory consumption means that even brief exposure to malicious files can cause system instability, particularly in resource-constrained environments or applications with limited memory allocation budgets.
Mitigation strategies should prioritize immediate upgrade to Pillow version 12.3.0 or later, which contains the necessary patch to properly reset component width calculations per tile boundary. Organizations should also implement input validation measures including file format verification and size limitations for image uploads, particularly in web-facing applications. Additional protective measures include deploying memory limits on processing containers, implementing sandboxed image processing environments, and establishing monitoring for unusual memory consumption patterns during image handling operations. The fix implemented in version 12.3.0 follows established security practices by ensuring proper scope management of accumulated variables and includes defensive programming techniques that prevent the type of cumulative calculation errors that led to this vulnerability. This remediation approach aligns with ATT&CK technique T1499.004 for resource hijacking, which addresses the exploitation of memory consumption vulnerabilities in software libraries.