CVE-2026-105932 in Pulsar
Summary
by MITRE • 10/22/2026
The Apache Pulsar broker admin REST API provides endpoints to read, set and remove the topic-level entry filter policy of a topic. For persistent topics these endpoints check that the caller is authorized for the entry filters topic policy operation. The corresponding endpoints for non-persistent topics (/admin/v2/non-persistent/{tenant}/{namespace}/{topic}/entryFilters) do not perform this authorization check. The only authorization check these endpoints perform is an indirect lookup permission check, made while the topic's partition metadata is retrieved; it is present in all affected versions.
As a result, when authentication and authorization are enabled, an authenticated user who has been granted produce or consume permission on a non-persistent topic, or on its namespace, but not permission to manage the topic's policies can read, replace or remove the topic-level entry filter policy of that topic. These operations should be restricted to users with the tenant admin role or the superuser role. This impact analysis assumes that Pulsar has been configured with the default authorization provider. For custom authorization providers, the impact could be slightly different.
The practical impact is limited by two broker configuration requirements, neither of which is met by default:
- Entry filters must have been installed by the operator. Entry filter implementations are loaded only at broker startup from the broker's entry filters directory, which is empty by default. A request can only select among entry filters the operator has already deployed; setting any other filter name is rejected. The issue does not allow a caller to install or load entry filter code or to run arbitrary code in the broker. - Topic-level entry filter policies must be allowed to override the broker-level configuration (allowOverrideEntryFilters, which is disabled by default). When this setting is disabled, the topic-level entry filter policy has no effect on message dispatch.
In deployments where both conditions are met, an unauthorized user can remove the topic-level entry filter policy of a non-persistent topic, for example one used to restrict which messages are delivered to consumers, or apply a different installed entry filter that withholds messages from subscriptions of that topic. Removing it makes the topic fall back to the namespace-level or broker-level entry filters, which are not removed. A changed policy affects only subscription dispatchers created after the change, for example for new subscriptions or when a subscription is re-created after all of its consumers have disconnected; dispatchers that already exist keep the entry filters they were created with. Because non-persistent topics do not store messages, messages withheld by an entry filter are not delivered. Reading the policy discloses only the names of the configured entry filters. The issue does not allow reading message contents, and entry filters cannot modify message payloads. Persistent topics and namespace-level entry filter policies are not affected. Apache Pulsar versions before 3.3.0 are not affected, because in those versions the entry filters topic policy check is made in code shared by the persistent and non-persistent endpoints.
This issue affects Apache Pulsar versions from 3.3.0 before 4.0.14 and from 4.1.0 before 4.2.5.
- 3.3.x and 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/.
Users who cannot upgrade immediately and have deployed entry filters should keep allowOverrideEntryFilters at its default value of false, so that topic-level entry filter policies do not affect message dispatch.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified in Apache Pulsar involves a critical authorization bypass within the broker admin REST API, specifically affecting non-persistent topics. The core technical flaw lies in the inconsistent implementation of access control checks between persistent and non-persistent topic endpoints. While the endpoints for persistent topics correctly verify that the caller is authorized to perform entry filters topic policy operations, the corresponding endpoints for non-persistent topics fail to execute this specific authorization check. Instead, these vulnerable endpoints rely solely on an indirect lookup permission check performed during the retrieval of the topic's partition metadata. This architectural inconsistency means that any authenticated user who possesses produce or consume permissions on a non-persistent topic, or its associated namespace, can inadvertently gain the ability to read, replace, or remove the topic-level entry filter policy without holding the necessary tenant admin or superuser roles required for such administrative actions.
This flaw is classified under CWE-862, which denotes Missing Authorization, as the system fails to enforce proper access controls on a protected resource. From an adversary perspective, this vulnerability aligns with MITRE ATT&CK techniques related to privilege escalation and unauthorized configuration changes, specifically allowing an attacker to manipulate security configurations within the messaging infrastructure. The practical impact of this flaw is contingent upon two specific broker configuration requirements that are not enabled by default in Apache Pulsar deployments. First, entry filters must have been installed by the operator at startup from a designated directory; since this directory is empty by default, users cannot load arbitrary code or execute malicious payloads on the broker through this vector. Second, the broker setting allowOverrideEntryFilters must be explicitly set to true, as it defaults to false. When disabled, topic-level entry filter policies have no effect on message dispatching, thereby neutralizing the impact of any unauthorized policy changes.
In environments where both conditions are met—entry filters are deployed and override permissions are enabled—an attacker can remove existing security controls or apply restrictive filters that withhold messages from specific subscriptions. Removing a topic-level entry filter causes the system to fall back to namespace-level or broker-level filters, which remain intact but may be less granular than the removed policy. Conversely, applying a different installed filter can restrict message delivery based on attributes defined by that filter. It is important to note that these changes only affect subscription dispatchers created after the modification; existing dispatchers retain their original entry filter configurations until they are recreated due to consumer disconnection or new subscription creation. The vulnerability does not permit reading message contents, nor can it modify message payloads directly, limiting the scope of data exposure primarily to the disclosure of configured entry filter names and the potential disruption of message delivery for specific subscriptions.
Persistent topics and namespace-level entry filter policies remain unaffected by this issue because they utilize a shared code path that correctly implements the necessary authorization checks. The vulnerability is present in Apache Pulsar versions from 3.3.0 up to, but not including, 4.0.14, as well as in versions from 4.1.0 up to, but not including, 4.2.5. In earlier versions prior to 3.3.0, the entry filters topic policy check was correctly implemented across both persistent and non-persistent endpoints, rendering them immune to this specific bypass. The lack of proper authorization in these affected releases represents a significant deviation from secure coding practices expected in enterprise-grade messaging systems, particularly when dealing with security-critical configuration parameters.
To mitigate this vulnerability, users operating on the affected version lines must upgrade immediately. Users running 3.3.x and 4.0.x versions should upgrade to at least version 4.0.14, while those on 4.1.x and 4.2.x versions should upgrade to at least version 4.2.5. For organizations unable to perform an immediate software upgrade due to operational constraints or compatibility requirements, a temporary mitigation strategy is available. Administrators can maintain the allowOverrideEntryFilters configuration parameter at its default value of false. This setting ensures that topic-level entry filter policies do not influence message dispatching, effectively neutralizing the impact of any unauthorized policy modifications made through the vulnerable endpoints. It is also recommended to review custom authorization providers if they are in use, as their specific implementations may alter the exact nature and scope of this vulnerability's impact compared to the default provider behavior described here.