CVE-2026-105938 — Apache Pulsar: Subscription authorization policies not enforced by namespace-level backlog and unsubscribe operations and by topic expire-all
Apache Pulsar namespaces can restrict which roles may use a subscription, either with the Prefix subscription authentication mode, which requires a subscription name to start with the role name, or by granting permission on a subscription to specific roles. Topic-level subscription operations, such as consuming, skipping messages, resetting a cursor or deleting a subscription, apply these subscription policies. Several admin REST API operations that act on subscriptions did not apply them: - the namespace-level and bundle-level clear backlog operations, both for a named subscription and for all subscriptions; - the namespace-level and bundle-level unsubscribe operations; - the topic-level operation that expires messages for all subscriptions of a topic. With the default authorization provider, the namespace-level operations require only consume permission granted on the namespace, and the expire-all operation requires only consume permission on the topic. As a result, when authentication and authorization are enabled and a namespace uses the Prefix subscription authentication mode or subscription permissions, an authenticated user with such consume permission can clear the backlog of, expire messages of, or delete a subscription that the policies would deny to that user. Tenant admin or superuser access is not required. The clear backlog operations can also be applied to the cursors used for geo-replication, so that messages not yet replicated to a remote cluster are skipped. Deployments that do not configure the Prefix subscription authentication mode or subscription permissions (the defaults) are not affected by this bypass, because consume permission on the namespace or topic already allows these operations there. This impact analysis assumes that Pulsar has been configured with the default authorization provider. For custom authorization providers, the impact could be different. The impact is on the integrity of subscription state. Clearing or expiring the backlog moves the subscription's cursor forward, so unacknowledged messages are no longer delivered to the subscription's consumers. The unsubscribe operation deletes a subscription that has no connected consumers. Skipped messages can be permanently deleted once no other subscription or the namespace's retention policy keeps them. The issue does not allow reading message contents, changing permissions or policies, or accessing other namespaces, and it does not affect the availability of the broker. In fixed versions, the namespace-level and bundle-level operations for a named subscription apply the subscription policies to that subscription, and the operations for all subscriptions, when requested by a user who is not a tenant admin or superuser, only act on the subscriptions that the user may access. Clearing the backlog of geo-replication cursors requires tenant admin or superuser access. Topic-level subscription operations apply the subscription policies for all types of authentication data, including that of the anonymous user role. This issue affects Apache Pulsar versions from 2.8.0 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. All brokers in a cluster must be upgraded before relying on the namespace-level restrictions, because brokers that have not been upgraded do not apply them when they receive the internal per-bundle requests. 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 can reduce exposure by restricting network access to the broker's admin REST API to trusted administrative clients.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.5% (30-day exploitation probability)+7
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Apache Pulsar).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Apache Software Foundation | Apache Pulsar | ≥ 2.8.0 and < 4.0.14≥ 4.1.0 and < 4.2.5 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 2.3 | CVSS 4.0 | Low | — | — | security@apache.org via NIST National Vulnerability Database |
| 2.3 | CVSS 4.0 | Low | — | — | apache via CVE Program (cve.org) e CISA ADP |
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/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 (score shown at the top: security@apache.org) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 22, 2026 → Oct 30, 2026 · 9 reading(s) · max 0.51%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Audit administrative actions and access to resources outside each user’s normal pattern.
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Source status changed · Received → Awaiting Analysis
- Source status changed · Published → Received
- Record published
- CVSS changed · 2.3
- Source status changed · → Published
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 22, 2026 – Oct 22, 2026
- 1× Official description updated · Oct 21, 2026 – Oct 21, 2026
References
5 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-105942 Apache Pulsar: Original principal of proxied requests authorized with the proxy's authentication data, allowing privilege escalation 10d
- High CVE-2026-105945 Apache Pulsar: Improper Validation of Package Name Components Allows Cross-Tenant Package Access in Filesystem Package Storage 10d
- High CVE-2026-105934 Apache Pulsar: Missing tenant admin authorization check when truncating a partitioned topic 10d
- Medium CVE-2026-105935 Apache Pulsar: Function trigger publishes to the input topic without checking the caller's produce permission 10d
- Medium CVE-2026-105936 Apache Pulsar: Functions connectors list endpoint does not apply the super-user check of the worker connectors endpoint 10d
- High CVE-2026-105937 Apache Pulsar: Missing authorization of the shadow topic source allows cross-tenant message disclosure and deletion of source topic data 10d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-105938 is "Apache Pulsar: Subscription authorization policies not enforced by namespace-level backlog and unsubscribe operations and by topic expire-all", rated Low. It affects Apache Pulsar (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 2.3 describes technical severity. EPSS 0.51% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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