CVE-2026-77121 in Nexus Repository
Summary
by MITRE • 09/02/2026
A user account with permission to deploy artifacts to a hosted Maven repository could upload a POM file containing an oversized metadata field. This causes future attempts to list or browse that repository's components to permanently fail until an administrator repairs the underlying data. Only the targeted repository is affected; other repositories and overall server health remain unaffected.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/02/2026
The vulnerability described constitutes a denial of service condition within hosted Maven repository management systems, specifically triggered by the ingestion of malformed metadata during artifact deployment. This flaw exploits the trust relationship between authenticated users with upload privileges and the repository's indexing or browsing mechanisms. When an authorized user uploads a Project Object Model file containing an excessively large metadata field, the system processes this input without adequate validation against size constraints relevant to its internal data structures used for listing components. The immediate technical consequence is that subsequent requests to list or browse the contents of the affected repository fail permanently until manual intervention occurs. This indicates that the malformed entry corrupts a persistent state variable or index structure within the database, rendering standard read operations impossible for that specific namespace without administrative repair.
From an architectural perspective, this issue highlights a failure in input validation and sanitization processes during the artifact ingestion pipeline. While the system correctly restricts write access to authorized users, it fails to enforce limits on metadata size relative to the storage format's capacity or performance thresholds. The impact is localized strictly to the targeted repository, preserving the integrity of other repositories and the overall server health. This isolation prevents a single malicious action from causing a global outage, but for the specific project or team relying on that repository, it results in a complete loss of visibility into available artifacts. Developers cannot resolve dependencies through standard browsing interfaces, potentially halting build processes if they rely on dynamic resolution rather than explicit version pinning.
In terms of industry standards classification, this vulnerability aligns with CWE-20 Improper Input Validation and CWE-400 Uncontrolled Resource Consumption. The oversized metadata field represents an input that exceeds the expected bounds for a specific data type or storage mechanism. Furthermore, it can be categorized under CWE-756 Missing Dynamic Memory Allocation Management if the system attempts to allocate memory based on user-supplied size without checking available resources. From a threat modeling perspective using MITRE ATT&CK, this behavior resembles T1498 Network Denial of Service, specifically through resource exhaustion or corruption techniques that disrupt service availability for specific targets rather than causing broad infrastructure failure. The attack vector requires authentication and write access, classifying it as an insider threat or compromised credential scenario rather than a remote unauthenticated exploit.
Mitigation strategies must focus on both preventive controls at the ingestion layer and reactive procedures for data repair. At the application level, developers should implement strict size limits on metadata fields within POM files during deployment validation. Any artifact containing metadata exceeding defined thresholds should be rejected with a clear error message before it is persisted to storage. Additionally, implementing schema validation tools that enforce maximum character counts or byte sizes for specific XML elements can prevent such malformed data from entering the system. For existing instances where corruption has occurred, administrators require scripts or manual database operations to identify and remove or truncate the offending metadata entries. Regular audits of repository integrity and monitoring for unusual spikes in artifact size during deployment can also serve as early warning indicators for this type of abuse.