CVE-2026-105945 in Pulsar
Summary
by MITRE • 10/21/2026
The Pulsar Packages Management Service can be configured to store packages on the local filesystem of the broker by using the filesystem storage provider. Package names consist of a type, tenant, namespace, name and version. Authorization of package operations is based only on the tenant and namespace, while the storage location of a package is derived from all of these components. The version component of a package name was not validated, so it could contain URL-encoded path separators and parent directory references. The filesystem storage provider resolved such a version to a location belonging to a package in a different tenant or namespace. Because that location is inside the configured storage directory, the containment check that the filesystem storage provider performs in recent releases did not prevent the access.
An authenticated user who has the packages permission on any namespace could use this to download, overwrite or delete packages stored in other tenants or namespaces for which the user has no permission. Packages overwritten or deleted in this way may be used by Pulsar Functions, Sources or Sinks, so the issue can affect the integrity and availability of these components. If authentication is disabled, the operations are available to any client that can reach the broker's admin REST API.
This issue only affects deployments in which package management is enabled with the broker setting enablePackagesManagement and the filesystem storage provider (FileSystemPackagesStorageProvider) is configured with the setting packagesManagementStorageProvider. Package management is disabled by default, and the default storage provider, which stores packages in Apache BookKeeper, is not affected.
This issue affects Apache Pulsar versions from 2.10.0 before 4.0.14 and from 4.1.0 before 4.2.5.
- 4.0.x version users should upgrade to at least 4.0.14. - 4.1.x and 4.2.x version users should upgrade to at least 4.2.5.
Users operating versions prior to those listed above should upgrade to the aforementioned patched versions or newer versions.
The currently supported Apache Pulsar release lines are 4.0.x and 5.0.x. The supported versions schedule is available at https://pulsar.apache.org/contribute/release-policy/.
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Analysis
by VulDB Data Team • 10/21/2026
Apache Pulsar, a distributed pub-sub messaging platform, contains a critical authorization bypass vulnerability within its Packages Management Service when configured to use the local filesystem storage provider. This flaw allows authenticated users with limited permissions to access, modify, or destroy packages belonging to other tenants and namespaces, effectively breaking the multi-tenant isolation model that is central to the system's security architecture. The root cause lies in how package identifiers are constructed and validated against the underlying file system structure. Package names consist of a type, tenant, namespace, name, and version component. While authorization checks for package operations rely solely on the tenant and namespace fields, the actual storage location on disk is derived from all five components, including the version string.
The technical flaw stems from insufficient validation of the version component within the package identifier. Specifically, the system fails to sanitize or validate this field against path traversal sequences such as URL-encoded path separators (e.g., %2F) and parent directory references (e.g., ..). When a malicious actor constructs a request with a crafted version string containing these elements, the filesystem storage provider resolves the resulting file path incorrectly. Instead of placing or retrieving the package within the expected subdirectory for that specific tenant and namespace, the system interprets the path traversal characters as instructions to move up the directory tree. This allows an attacker to target files located in directories associated with different tenants or namespaces. Although recent releases include a containment check intended to prevent access outside the configured storage root, this validation logic was either absent or insufficiently robust against these specific encoded bypass techniques during the affected versions, allowing the malicious path resolution to succeed.
The operational impact of this vulnerability is severe due to its effect on data integrity and availability across multi-tenant environments. An authenticated user who possesses only basic packages permissions on any single namespace can exploit this flaw to download sensitive package artifacts from other tenants, potentially leading to information disclosure if those packages contain proprietary code or configuration details. More critically, the attacker can overwrite or delete packages stored in unauthorized tenant namespaces. Since Apache Pulsar Functions, Sources, and Sinks frequently rely on these packaged dependencies for execution, tampering with them can disrupt service availability or introduce malicious logic into running functions. This represents a significant risk to system stability and trustworthiness, as it undermines the fundamental assumption that tenants are isolated from one another within the same cluster.
From a threat modeling perspective, this vulnerability aligns with CWE-284 Improper Access Control and CWE-22 Path Traversal: '..' Sequence. It also maps to MITRE ATT&CK techniques related to Lateral Movement or Data Manipulation depending on whether the attacker is moving between tenants or altering data integrity. The attack vector requires authentication, meaning it falls under T1078 Valid Accounts if valid credentials are compromised, but since any authenticated user with minimal permissions can exploit this, it highlights a failure in privilege separation and input validation at the application logic layer rather than just network-level access control. If authentication is disabled on the broker's admin REST API, the vulnerability becomes accessible to any client that can reach the service, escalating the risk from an insider threat or compromised account scenario to a remote unauthenticated attack vector.
Mitigation strategies focus primarily on upgrading to patched versions of Apache Pulsar where this logic has been corrected and input validation is enforced strictly for all components of the package identifier. Users running version 4.0.x must upgrade to at least 4.0.14, while those on 4.1.x or 4.2.x should upgrade to at least 4.2.5. For organizations unable to immediately patch their production environments due to compatibility constraints, temporary mitigations include disabling the filesystem storage provider in favor of the default Apache BookKeeper backend, which is not affected by this specific path traversal issue. Additionally, ensuring that authentication and authorization are strictly enforced on all administrative endpoints reduces the attack surface for unauthenticated exploitation attempts. Organizations should also review their package management configurations to ensure that enablePackagesManagement is set appropriately and consider implementing additional WAF rules or proxy-level filtering to block requests containing encoded path sequences if immediate patching is not feasible.