CVE-2026-105926 Apache Software Foundation CVE debrief

Who should care

Defenders responsible for Apache Pulsar instances, especially those exposed to untrusted or authenticated clients, should assess exposure and prioritize remediation. This includes verifying and remediating vulnerable instances, reviewing compensating controls for exposed systems, and monitoring for suspicious schema registration or retrieval activity.

Why it matters

CVE-2026-105926 allows authenticated Apache Pulsar clients to read or register schemas for topics they are not authorized for, potentially disclosing schema information or affecting legitimate producers and consumers. Defenders should verify and remediate vulnerable instances.

• Authenticated clients can read schema definitions for topics in other namespaces or tenants
• Authenticated clients can register new schema versions for existing topics in other namespaces or tenants
• Schema compatibility and auto-update policies still apply to registered schema versions
• Verification of vulnerable versions, exposure, and remediation is required

Technical summary

Apache Pulsar's binary protocol GetSchema and GetOrCreateSchema commands do not check client authorization for the target topic, allowing authenticated clients without permissions to read or register schemas for topics in other namespaces or tenants. This vulnerability can lead to unauthorized access to schema information and potential disruptions to legitimate producers and consumers. The issue affects the Pulsar broker's handling of these commands, which do not check client authorization for the target topic, unlike other topic commands.

Defensive priority

Defenders should prioritize verifying and remediating vulnerable Apache Pulsar instances, especially those exposed to untrusted or authenticated clients.

Recommended defensive actions

• Verify Apache Pulsar instance version and exposure to untrusted or authenticated clients
• Check and enforce topic authorization for GetSchema and GetOrCreateSchema commands
• Monitor for suspicious schema registration or retrieval activity
• Apply vendor-provided patches or updates for vulnerable Apache Pulsar versions
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability, affected versions, and vendor advisories. However, additional information on exploitation or victim impact is not available. Defenders should verify and remediate vulnerable instances, especially those exposed to untrusted or authenticated clients, and review compensating controls for exposed systems while remediation is scheduled and verified.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.