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Response snapshot Oct 27, 2026, 01:11 UTC

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VulnerabilityCVE-2026-105937

Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger.

Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. The source topic is selected by setting the reserved topic property PULSAR.SHADOW_SOURCE.

At a glance

Exploited
Not known
Severity
8.7 High (CVSS 4.0)
Chance of exploitation
0.2% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-105937 (opens a new tab)

What happened

Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. The source topic is selected by setting the reserved topic property PULSAR.SHADOW_SOURCE. The admin REST API accepts this property when creating a non-partitioned or partitioned topic and when updating the properties of an existing topic.

On these paths the broker authorizes the caller only against the topic being created or updated. It does not authorize the caller against the source topic named in the property. The existing authorization for shadow topic configuration (the SHADOW_TOPIC topic policy on the source topic) is applied only to the source-side shadow topics admin API, not to these paths.

As a result, an authenticated user who is allowed to create topics or update topic properties in one tenant can bind a topic in that tenant to a persistent topic in any other tenant. With the default authorization provider, these operations require the tenant admin role for the user's own tenant. The user does not need any permission on the source topic, its namespace or its tenant.

This impact analysis assumes that Pulsar has been configured with the default authorization provider. For custom authorization providers, the impact could be different.

Continue reading

The user can then consume from the shadow topic, using only permissions on their own topic, and receive retained messages that were published to the source topic in the other tenant. Exposure is limited to messages that are still retained and readable in the source topic's ledgers; messages protected with client-side end-to-end encryption cannot be decrypted without the encryption keys.

A producer on the shadow topic can also register a new schema version under the source topic's schema, subject to the schema compatibility settings; existing schema versions are not replaced.

In addition, the shadow topic's managed ledger applies its own retention, trimming, offloading and deletion to the source topic's ledgers. This can permanently delete the source topic's ledger data from BookKeeper and from tiered storage, regardless of the source topic's own subscriptions and retention policy, including messages that have not yet been acknowledged.

Deleting the shadow topic can also delete the source topic's ledgers. This data loss can also affect shadow topics that were configured intentionally by administrators.

This issue affects Apache Pulsar versions from 3.0.0 before 4.0.14 and from 4.1.0 before 4.2.5. Apache Pulsar 2.x releases do not contain the shadow topic implementation.

- 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/.

In the fixed versions, shadow topics are disabled by default and are controlled by the new broker configuration setting enableShadowTopics (default false). While it is disabled, the broker rejects creating shadow topics, setting the PULSAR.SHADOW_SOURCE property, and loading or replicating to existing shadow topics.

Deployments that use shadow topics must set enableShadowTopics=true in the broker configuration of all brokers after upgrading; otherwise existing shadow topics will not be loaded. When shadow topics are enabled, binding a shadow topic to a source topic in a different tenant requires the superuser role.

The fixed versions also prevent a shadow topic from deleting or trimming the ledgers and offloaded data of its source topic.

Affected versions provide no configuration option to disable shadow topics. Users who cannot upgrade immediately can reduce exposure by granting the tenant admin role only to trusted principals.

Scores and how they were measured

CVSS base severity

8.7

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:N/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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.2%

Scored Percentile 15.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-105937 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-105937, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. (CVE-2026-105937). https://kevwire.com/record/CVE-2026-105937

MLA

"Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. (CVE-2026-105937)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-105937.

Chicago

KEVWire. "Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. (CVE-2026-105937)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-105937.

Evidence summary (plain text)

Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. (Oct 21, 2026).
Apache Pulsar shadow topics (PIP-180) are topics that read the stored messages of a source topic from that topic's managed ledger. The source topic is selected by setting the reserved topic property PULSAR.SHADOW_SOURCE. The admin REST API accepts this property when creating a non-partitioned or partitioned topic and when updating the properties of an existing topic. On these paths the broker authorizes the caller only against the topic being created or updated. It does not authorize the caller against the source topic named in the property. The existing authorization for shadow topic configuration (the SHADOW_TOPIC topic policy on the source topic) is applied only to the source-side shadow topics admin API, not to these paths.

As a result, an authenticated user who is allowed to create topics or update topic properties in one tenant can bind a topic in that tenant to a persistent topic in any other tenant. With the default authorization provider, these operations require the tenant admin role for the user's own tenant. The user does not need any permission on the source topic, its namespace or its tenant. This impact analysis assumes that Pulsar has been configured with the default authorization provider. For custom authorization providers, the impact could be different.

The user can then consume from the shadow topic, using only permissions on their own topic, and receive retained messages that were published to the source topic in the other tenant. Exposure is limited to messages that are still retained and readable in the source topic's ledgers; messages protected with client-side end-to-end encryption cannot be decrypted without the encryption keys. A producer on the shadow topic can also register a new schema version under the source topic's schema, subject to the schema compatibility settings; existing schema versions are not replaced.

In addition, the shadow topic's managed ledger applies its own retention, trimming, offloading and deletion to the source topic's ledgers. This can permanently delete the source topic's ledger data from BookKeeper and from tiered storage, regardless of the source topic's own subscriptions and retention policy, including
CVSS 8.7 (version 4.0; evidence as of Oct 23, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-105937).
EPSS 0.2% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-105937&date=2026-10-26).
Sources:
NVD CVE-2026-105937: https://nvd.nist.gov/vuln/detail/CVE-2026-105937
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=8000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-105937&date=2026-10-26
Record ID: CVE-2026-105937.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

NVD status: Awaiting Analysis. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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