CVE-2026-47893 Overview
CVE-2026-47893 affects Spring Framework applications that use Spring WebFlux with WebSocket support. The vulnerability causes the framework to include incoming request headers in the reason field of exceptions raised during WebSocket handling. Because exception reasons can propagate to logs, error responses, or downstream handlers, sensitive header values such as authorization tokens, cookies, or API keys may be exposed indirectly. The issue is an information disclosure weakness [CWE-200] rather than a code execution flaw. It affects multiple maintained release trains of Spring Framework, requiring coordinated patching across enterprise Java applications.
Critical Impact
Request headers, including credentials and session tokens, can leak into exception reasons produced by Spring WebFlux WebSocket handlers.
Affected Products
- Spring Framework 7.0.0 through 7.0.8
- Spring Framework 6.2.0 through 6.2.19, 6.1.0 through 6.1.28, and 6.0.0 through 6.0.30
- Spring Framework 5.3.0 through 5.3.49, and 5.2.25.RELEASE and earlier
Discovery Timeline
- 2026-08-27 - CVE-2026-47893 published to the National Vulnerability Database
- 2026-08-27 - Last updated in NVD database
Technical Details for CVE-2026-47893
Vulnerability Analysis
Spring WebFlux is the reactive web stack in the Spring Framework. When a WebFlux application accepts WebSocket connections, the framework processes the initial HTTP upgrade request and its headers before establishing the WebSocket session. During this handshake and subsequent handling, failure paths can raise exceptions that include request header values in the exception reason string.
Exception reason strings are commonly written to application logs, forwarded to observability platforms, returned in error frames, or surfaced by generic error handlers. Any of these downstream consumers may then persist or expose data that the header carried. Because WebSocket handshakes routinely include Authorization, Cookie, Sec-WebSocket-Protocol, and custom authentication headers, the leaked material often carries direct authentication value.
Root Cause
The root cause is unsafe construction of exception reason messages inside the WebFlux WebSocket handling path. The framework concatenates untrusted request header content into a diagnostic string without redaction. This violates the principle of separating diagnostic context from sensitive input.
Attack Vector
An attacker does not directly trigger the disclosure to themselves. Instead, sensitive headers belonging to legitimate users leak into logs or error surfaces accessible to operators, log aggregators, or any actor with access to those systems. An attacker who already has read access to logs or error output can then harvest credentials from other users' sessions. The vulnerability can also be provoked by crafting requests that reliably trigger the exception path, amplifying the volume of leaked headers.
No verified exploit code is published. Refer to the Spring Security Advisory CVE-2026-47893 for authoritative technical details.
Detection Methods for CVE-2026-47893
Indicators of Compromise
- Application logs containing HTTP header names such as Authorization, Cookie, or X-Api-Key inside exception messages emitted from Spring WebFlux WebSocket handling classes.
- Error responses or WebSocket close frames whose reason strings contain header-like key-value pairs.
- Log aggregation queries surfacing bearer tokens or session identifiers in stack traces originating from org.springframework.web.reactive.socket packages.
Detection Strategies
- Inventory running services to identify Spring Framework versions in the affected ranges and confirm which applications enable WebFlux WebSocket endpoints.
- Search centralized logs for stack traces referencing WebFlux WebSocket handlers alongside header token patterns such as Bearer , JSESSIONID=, or Basic .
- Review error-handling middleware to determine whether exception reason strings are echoed to clients or forwarded to third-party monitoring services.
Monitoring Recommendations
- Enable structured logging with field-level redaction for HTTP header values across reactive services.
- Alert on log events that combine WebSocket handshake failures with token or cookie patterns.
- Restrict access to log platforms and audit historical log data for previously leaked credentials that must be rotated.
How to Mitigate CVE-2026-47893
Immediate Actions Required
- Upgrade Spring Framework to a fixed maintenance release per the vendor advisory before continuing to expose WebFlux WebSocket endpoints.
- Rotate any credentials, session tokens, and API keys that may have been captured in logs during the exposure window.
- Restrict and audit access to log storage, SIEM ingestion pipelines, and error reporting services that received WebFlux exception output.
Patch Information
Spring publishes fixed versions and remediation guidance in the Spring Security Advisory CVE-2026-47893. Apply the latest patched release on each affected 5.3.x, 6.0.x, 6.1.x, 6.2.x, and 7.0.x train, and rebuild dependent applications so the corrected framework classes are deployed.
Workarounds
- Configure a global exception handler that scrubs or replaces exception reason strings before they are logged, returned, or forwarded.
- Apply log redaction filters that mask common credential header patterns at ingestion time.
- Disable or restrict WebSocket endpoints in affected WebFlux applications until the framework is upgraded.
# Configuration example
# Refer to the Spring Security Advisory for authoritative upgrade guidance:
# https://spring.io/security/cve-2026-47893
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
