Security readout for executives and security teams
Plain-English summary
CVE-2026-39304 can let an unauthenticated network client crash an Apache ActiveMQ service by exhausting broker memory through TLS handling. The business impact is availability loss for messaging-dependent systems, not data theft or code execution based on the provided sources.
Executive priority
Treat as a prompt availability fix for any production ActiveMQ service supporting critical workflows. Prioritize internet-facing or broadly reachable brokers first. The issue is high severity because outage can be triggered remotely, but provided evidence does not support data compromise or confirmed exploitation.
Technical view
ActiveMQ NIO SSL transports mishandle TLSv1.3 KeyUpdate events triggered by clients. Repeated updates can consume SSL engine memory until the broker hits out-of-memory denial of service. Affected products include ActiveMQ Client, Broker, All, and Apache ActiveMQ before the fixed vendor-recommended releases.
Likely exposure
Exposure is most likely where Apache ActiveMQ NIO SSL transports are reachable by clients, especially over TLSv1.3. The source bundle identifies affected Maven artifacts including activemq-client, activemq-broker, activemq-all, and apache-activemq in vulnerable version ranges.
Exploitation context
CVSS indicates network attack vector, low complexity, no privileges, and no user interaction. The bundle does not show CISA KEV listing or active exploitation evidence, so active exploitation should not be assumed.
Researcher notes
The core weakness is resource exhaustion from incorrect TLS KeyUpdate handling in NIO SSL transport. TLS versions before 1.3 are described as broken but not OOM-vulnerable. Avoid assuming exploit maturity beyond the advisory and CVSS metadata.
Mitigation direction
- Upgrade to Apache ActiveMQ 6.2.4 or 5.19.5 per vendor guidance.
- Patch affected activemq-client, activemq-broker, activemq-all, and apache-activemq dependencies.
- Limit NIO SSL broker exposure to trusted networks while upgrades are scheduled.
- Review Apache and Red Hat advisories for any environment-specific guidance.
- Monitor broker memory pressure and restart events until remediation is complete.
Validation and detection
- Inventory deployed ActiveMQ versions and Maven artifacts across applications and brokers.
- Confirm whether NIO SSL transports are enabled and reachable by clients.
- Verify TLSv1.3 is in use on exposed ActiveMQ SSL endpoints.
- Check broker logs and metrics for out-of-memory or SSL engine failures.
- After upgrade, confirm runtime reports version 6.2.4 or 5.19.5.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-400: Exact CWE lookup
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Open ATT&CK lookupCWE-770: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-39304 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-04-10T11:00:59.088Z: Reported to Red Hat.
- 2026-04-10T10:54:04.130Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://activemq.apache.org/security-advisories.data/CVE-2026-39304-announcement.txtCVE reference, apache · vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-39304CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2457275CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39304.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Allocation of Resources Without Limits or Throttling
Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.