CVE-2026-54225: Apache CXF Denial of Service Vulnerability

CVE-2026-54225 Overview

CVE-2026-54225 affects Apache CXF, an open-source services framework used to build and develop web services. The vulnerability stems from the absence of a default value for the attachment-max-size property. Without an explicit limit set by the user, remote attackers can submit oversized attachments and trigger resource exhaustion. This condition maps to [CWE-770] Allocation of Resources Without Limits or Throttling. Apache CXF versions prior to 4.2.3, 4.1.8, and 3.6.12 are affected.

Critical Impact
Remote attackers can send unbounded attachments to Apache CXF endpoints, causing denial of service through memory or disk exhaustion on the target service.

Affected Products

Apache CXF versions prior to 4.2.3 (4.2.x branch)
Apache CXF versions prior to 4.1.8 (4.1.x branch)
Apache CXF versions prior to 3.6.12 (3.6.x branch)

Discovery Timeline

2026-08-06 - CVE-2026-54225 published to NVD
2026-08-06 - Last updated in NVD database

Technical Details for CVE-2026-54225

Vulnerability Analysis

Apache CXF processes SOAP and REST messages that can include MIME attachments. The framework exposes the attachment-max-size property to constrain the size of incoming attachments. In versions before 4.2.3, 4.1.8, and 3.6.12, this property carried no default value. Administrators who did not explicitly configure the property left CXF endpoints willing to accept attachments of arbitrary size. An attacker can exploit this to submit large payloads that consume memory, disk, or CPU resources on the server. The upstream fix imposes a 50 MB default limit, aligning behavior with the safer configuration expected by most deployments.

Root Cause

The root cause is a missing safe default in the attachment processing configuration. CXF relied on operator-supplied limits rather than shipping a conservative built-in value. This design choice created an unsafe-by-default posture for any deployment that did not review the property.

Attack Vector

An unauthenticated remote attacker sends crafted SOAP or REST requests containing very large MIME attachments to a vulnerable CXF endpoint. The service allocates buffers to process the attachment without bounding the size. Repeated requests amplify the effect and can degrade or crash the target service. No authentication or user interaction is required when the endpoint is publicly reachable.

See the Apache Mailing List Thread for the maintainers' announcement and technical context.

Detection Methods for CVE-2026-54225

Indicators of Compromise

Unusually large multipart or MIME attachments arriving at CXF-hosted SOAP or REST endpoints.
Repeated high-volume requests from a single source that correlate with spikes in JVM heap usage or disk consumption.
Application logs showing OutOfMemoryError or attachment processing timeouts near the affected services.

Detection Strategies

Inventory running Java services and identify Apache CXF versions using dependency scans or SBOM tooling.
Instrument web application firewalls or reverse proxies to log request body sizes for CXF endpoints.
Correlate JVM memory pressure alerts with inbound traffic patterns to identify attachment-based abuse.

Monitoring Recommendations

Track request size distributions on service endpoints and alert on statistical outliers.
Monitor JVM garbage collection frequency and heap saturation on hosts running CXF workloads.
Log and review CXF configuration at startup to confirm attachment-max-size is set to an intentional value.

How to Mitigate CVE-2026-54225

Immediate Actions Required

Upgrade Apache CXF to 4.2.3, 4.1.8, or 3.6.12 depending on the branch in use.
Explicitly configure the attachment-max-size property on every CXF endpoint until upgrades are complete.
Place CXF services behind a reverse proxy or WAF that enforces maximum request body size.

Patch Information

Apache CXF releases 4.2.3, 4.1.8, and 3.6.12 remediate the issue by imposing a default attachment size limit of 50 MB. Users who require a different threshold should still set attachment-max-size explicitly. Consult the Apache Mailing List Thread for release details.

Workarounds

Set attachment-max-size to a conservative value in CXF endpoint configuration if immediate patching is not feasible.
Enforce request size limits at the ingress layer using Nginx client_max_body_size or Apache HTTPD LimitRequestBody.
Restrict network exposure of CXF endpoints to authenticated clients until the upgrade is applied.

bash

# Configuration example: enforce attachment size limit on a CXF endpoint
# Spring configuration snippet
# <jaxws:endpoint id="myService" implementor="#serviceBean" address="/service">
#   <jaxws:properties>
#     <entry key="attachment-max-size" value="52428800"/>
#   </jaxws:properties>
# </jaxws:endpoint>

# Nginx ingress hardening
# server {
#   client_max_body_size 50m;
# }