CVE-2026-27980 in next.js
Summary
by MITRE • 03/18/2026
Next.js is a React framework for building full-stack web applications. Starting in version 10.0.0 and prior to version 16.1.7, the default Next.js image optimization disk cache (`/_next/image`) did not have a configurable upper bound, allowing unbounded cache growth. An attacker could generate many unique image-optimization variants and exhaust disk space, causing denial of service. This is fixed in version 16.1.7 by adding an LRU-backed disk cache with `images.maximumDiskCacheSize`, including eviction of least-recently-used entries when the limit is exceeded. Setting `maximumDiskCacheSize: 0` disables disk caching. If upgrading is not immediately possible, periodically clean `.next/cache/images` and/or reduce variant cardinality (e.g., tighten values for `images.localPatterns`, `images.remotePatterns`, and `images.qualities`).
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Analysis
by VulDB Data Team • 03/23/2026
The vulnerability described in CVE-2026-27980 represents a critical denial of service weakness within the Next.js framework that has significant implications for web application security and system stability. This issue affects Next.js versions 10.0.0 through 16.1.6, where the default image optimization feature lacks proper resource management controls. The problem manifests through the `/_next/image` endpoint which serves as the default disk cache location for optimized images, creating an environment where attackers can exploit the absence of cache size limitations to consume excessive system resources.
The technical flaw stems from the absence of configurable upper bounds on the disk cache used for image optimization operations. This design oversight allows for unbounded cache growth, meaning that any client can generate an unlimited number of unique image optimization variants without triggering automatic cleanup mechanisms. The vulnerability operates by leveraging the image optimization API to create numerous distinct cache entries through variations in image parameters such as size, format, quality, and other transformation attributes. Each unique combination results in a separate cache entry, enabling attackers to rapidly fill available disk space with these optimization artifacts.
From an operational impact perspective, this vulnerability creates a severe denial of service condition that can render affected web applications completely inaccessible to legitimate users. When disk space becomes exhausted due to the uncontrolled cache growth, the application cannot process new image optimization requests, leading to service disruption and potential system instability. The attack vector is particularly concerning because it requires minimal privileges and can be executed through normal API usage patterns, making it difficult to distinguish from legitimate traffic. The vulnerability also impacts system performance by consuming storage resources that could otherwise be allocated to application operations, database transactions, or other critical system functions.
The fix implemented in Next.js version 16.1.7 addresses this issue through the introduction of an LRU (Least Recently Used) backed disk cache with configurable maximum size limits. This solution incorporates the `images.maximumDiskCacheSize` parameter that allows administrators to define explicit cache boundaries, enabling automatic eviction of older entries when size limits are exceeded. The implementation follows established security patterns for resource management and prevents unbounded growth through proper cache lifecycle management. Additionally, the solution provides a mechanism to completely disable disk caching by setting `maximumDiskCacheSize: 0`, offering flexibility for environments with specific security requirements or resource constraints. The mitigation strategy also includes recommended workarounds for organizations unable to upgrade immediately, such as periodic manual cleanup of the `.next/cache/images` directory and reducing the cardinality of image optimization variants through tighter configuration of `images.localPatterns`, `images.remotePatterns`, and `images.qualities` parameters.
This vulnerability aligns with CWE-400, which addresses uncontrolled resource consumption, and represents a classic example of insufficient resource management in web applications. The attack pattern follows ATT&CK technique T1499.004 for network denial of service, where attackers leverage application features to consume system resources. The security implications extend beyond simple resource exhaustion to include potential system instability and service disruption that can affect business continuity and user experience. Organizations implementing Next.js applications must prioritize this vulnerability remediation as part of their security maintenance procedures to prevent exploitation and ensure application availability. The fix demonstrates proper security engineering principles through the implementation of configurable resource limits and automatic cleanup mechanisms that prevent similar vulnerabilities from occurring in future versions of the framework.