Apache Pulsar: Incorrect Authorization
CVE-2026-105942 is a high-severity incorrect authorization vulnerability in Apache Pulsar from Apache, with a CVSS 4.0 base score of 7.7 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 4.0.14, 4.2.5 as the first without the flaw, so updating Apache Pulsar to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Apache Pulsar to 4.0.14 or 4.2.5, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Pulsar | 2.8.1 up to, but not including, 4.0.14; 4.1.0 up to, but not including, 4.2.5 | 4.0.14, 4.2.5 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- PresentThe target must be in a specific state or configuration for the attack to work.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- NoneNo loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- NoneNo loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- NoneNo loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (apache.org).
Official description
When a configured proxy role sends a request to the broker on behalf of another user (the original principal), the broker is designed to authorize both the proxy role and the original principal and to allow the request only if both are authorized, so that the original principal cannot exceed its own permissions. Two flaws weakened this check. First, the original principal was authorized with the proxy's authentication data instead of its own. On the admin REST API of the broker and the functions worker, this applied to every proxied request. On the Pulsar binary protocol, it applied when the proxy did not forward the client's credentials to the broker, which was the default of the Pulsar proxy in the affected versions. Authorization providers that resolve permissions from the role name only, such as the default authorization provider, are not affected by this flaw. The multi-role token authorization provider (MultiRolesTokenAuthorizationProvider), added in Apache Pulsar 2.8.1, resolves roles from the role claim of the token in the authentication data it is given. When a proxy authenticates to the broker with its own token, the original principal was therefore authorized with all roles in the proxy's token. If any of those roles is a superuser or tenant admin role, any user whose requests are forwarded by that proxy can perform operations that need those permissions without holding them. Custom authorization providers that use the authentication data could be affected in a similar way. Second, independently of the authorization provider, the tenant admin check of a proxied admin REST API request succeeded without checking the original principal when the proxy role was itself an admin role of the tenant. In deployments where a proxy role is a tenant admin, including with the default authorization provider, any user whose requests are forwarded by that proxy could perform tenant administration operations on that tenant. This behavior is present from 2.8.4 in the 2.8.x releases, from 2.9.3 in the 2.9.x releases, and from 2.10.1 onwards. Deployments that use neither the multi-role token authorization provider nor a custom provider that uses the authentication data are not affected by the first flaw, and with the multi-role token authorization provider, neither are deployments whose proxies do not authenticate to the broker with a token. Deployments in which no proxy role is listed as an admin role of a tenant are not affected by the second flaw. A proxy role that is a superuser but is not listed as a tenant admin does not trigger it, because the tenant admin check of the built-in authorization providers only considers the tenant's admin roles; this can differ for custom authorization providers that treat superusers as tenant admins. In fixed versions, both the proxy role and the original principal are authorized for each proxied request, and the original principal is authorized only with its own authentication data. With the multi-role token authorization provider, the roles of a forwarded token are used for the original principal only when that token authenticates as the original principal; otherwise only the original principal's role name is used. For tenant admin checks, the proxy role and the original principal must each be a superuser or a tenant admin of the tenant. This issue affects Apache Pulsar versions from 2.8.1 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/.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
How developers prevent this class of flaw
- Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework and the OWASP ESAPI Access Control feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Apache Pulsar
- 7.7 High severity
- 8.7 High severity
- 7.2 High severity
- 9.2 Critical severity
- 8.8 High severity
- 9.9 Critical severity
Recent Incorrect Authorization vulnerabilities
- 10.0 Critical severity
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.1 High severity
- 9.1 Critical severity
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