CVE-2026-42886 in audiobookshelf
Summary
by MITRE • 05/11/2026
Audiobookshelf is a self-hosted audiobook and podcast server. Prior to 2.32.2, the POST /api/backups/upload endpoint decompresses the details entry from an uploaded .audiobookshelf ZIP file entirely into memory using zip.entryData(), with no limit on the decompressed size. The upload middleware also has no file size limit. An admin user can upload a crafted ZIP containing a highly compressed details entry that, when decompressed, consumes hundreds of megabytes or gigabytes of memory, crashing the server process via out-of-memory. This vulnerability is fixed in 2.32.2.
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Analysis
by VulDB Data Team • 05/12/2026
The vulnerability in Audiobookshelf affects versions prior to 2.32.2 and represents a critical memory exhaustion issue within the backup upload functionality. The flaw exists in the POST /api/backups/upload endpoint which processes uploaded ZIP files containing audiobook and podcast data. When administrators upload backup files, the system decompresses the details entry from these archives directly into memory using the zip.entryData() function without any size limitations on the decompressed content. This design flaw creates an avenue for malicious actors to exploit the system through carefully crafted archive files that contain highly compressed data within the details entry.
The technical implementation of this vulnerability stems from inadequate input validation and memory management practices within the application's file processing pipeline. The zip.entryData() function processes the decompressed data entirely in memory without enforcing size constraints, allowing attackers to craft ZIP files containing compressed entries that expand to enormous sizes when decompressed. Combined with the absence of file size limits in the upload middleware, this creates a perfect storm for memory exhaustion attacks. The vulnerability specifically targets the details entry within the ZIP archive structure, which typically contains metadata about the audiobook collection, but can be manipulated to consume excessive system resources during decompression.
The operational impact of this vulnerability is severe and directly affects system stability and availability. An authenticated administrator user can trigger a denial of service condition by uploading a maliciously crafted ZIP file that consumes hundreds of megabytes or even gigabytes of server memory. When the decompression process exceeds available memory resources, the server process crashes and becomes unavailable to legitimate users. This represents a privilege escalation vulnerability since it requires admin-level access but results in a system-wide outage that affects all users of the audiobook server. The attack vector is particularly concerning because it can be executed through normal administrative functions without requiring specialized tools or techniques beyond creating a specific ZIP archive.
This vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and specifically manifests as a memory exhaustion issue that can lead to application crashes and system instability. The flaw also relates to ATT&CK technique T1499.004, which covers "Toggle System Details Visibility" and can be leveraged to disrupt service availability through resource exhaustion attacks. The vulnerability demonstrates poor input validation practices and inadequate resource management that violates fundamental security principles for handling untrusted data. The fix implemented in version 2.32.2 addresses these issues by introducing proper size limits and memory constraints during the decompression process, ensuring that uploaded backup files cannot consume excessive system resources. Organizations should prioritize updating to version 2.32.2 or later to remediate this vulnerability and prevent potential exploitation that could result in service disruption and data accessibility issues.