Cloudreve up to 4.17.x Storage upload.go PrepareUpload resource consumption

Summaryinfo

A vulnerability was found in Cloudreve up to 4.17.x. It has been declared as problematic. Impacted is the function PrepareUpload of the file pkg/filemanager/fs/dbfs/upload.go of the component Storage. Such manipulation leads to resource consumption. This vulnerability is uniquely identified as CVE-2026-77633. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Cloudreve up to 4.17.x. Affected by this issue is the function PrepareUpload of the file pkg/filemanager/fs/dbfs/upload.go of the component Storage. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. CVE summarizes:

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, PrepareUpload in pkg/filemanager/fs/dbfs/upload.go checks a stale in-memory user storage value through validateUserCapacity and later applies an unconditional storage charge outside the same quota-enforcing transaction. An authenticated user with Files.Write permission can issue concurrent upload-session requests that read the same capacity snapshot, all pass the MaxStorage check, and reserve their declared sizes through CommitWithStorageDiff. The resulting reservations can exceed the account quota and can be materialized as chunked uploads that exhaust host storage and deny uploads to other users. The default local-storage policy and default User group are affected. This issue is fixed in version 4.18.0.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-77633 since 08/20/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 4.18.0 eliminates this vulnerability.

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Productinfo

Type

• Cloud Software

Name

• Cloudreve

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17

Website

• Product: https://github.com/cloudreve/cloudreve/

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