Answer in brief
CVE-2026-33249 records a Medium severity (CVSS 4.3) vulnerability in NATS: Message tracing can be redirected to arbitrary subject. The current sources do not mark it as known exploited. The current feed maps github.com/nats-io/nats-server/v2 (go), github.com/nats-io/nats-server/v2 (go). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps github.com/nats-io/nats-server/v2 (go), github.com/nats-io/nats-server/v2 (go). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/nats-io/nats-server/v2go | >=2.11.0 <2.11.15 | 2.11.15 |
| github.com/nats-io/nats-server/v2go | >=2.12.0-preview.1 <2.12.6 | 2.12.6 |
Published upstream
Mar 24, 2026
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Sep 10, 2026
### Background NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing. The nats-server supports telemetry on messages, using the per-message NATS headers. ### Problem Description A valid client which uses message tracing headers can indicate that the trace messages can be sent to an arbitrary valid subject, including those to which the client does not have publish permission. The payload is a valid trace message and not chosen by the attacker. ### Affected Versions Any version before v2.12.6 or v2.11.15 ### Workarounds None.
Quoted source text, attributed separately from HOL analysis.