CVE-2026-11722: IBM WebSphere HTTP Request Smuggling Flaw

CVE-2026-11722 Overview

CVE-2026-11722 is an HTTP request smuggling vulnerability affecting IBM WebSphere Application Server and WebSphere Application Server Liberty. The flaw is categorized under [CWE-444] Inconsistent Interpretation of HTTP Requests. Attackers can exploit the vulnerability over the network without authentication or user interaction, though successful exploitation requires overcoming high attack complexity. The issue allows limited impact to confidentiality and integrity of proxied traffic. IBM has published guidance on its support portal.

Critical Impact
Successful exploitation can enable an attacker to smuggle crafted HTTP requests past front-end proxies, potentially bypassing access controls, poisoning caches, or accessing sensitive request data handled by WebSphere.

Affected Products

IBM WebSphere Application Server
IBM WebSphere Application Server Liberty
Deployments fronted by proxies or load balancers that parse HTTP differently than WebSphere

Discovery Timeline

2026-09-18 - CVE-2026-11722 published to NVD
2026-09-22 - Last updated in NVD database

Technical Details for CVE-2026-11722

Vulnerability Analysis

HTTP request smuggling occurs when a front-end HTTP intermediary and a back-end server disagree on where one request ends and the next begins. The affected WebSphere and WebSphere Liberty components parse ambiguous Content-Length and Transfer-Encoding headers in a way that diverges from upstream proxies. This desynchronization lets an attacker prepend attacker-controlled bytes onto a subsequent request from another user.

Exploitation is network-reachable with no privileges or user interaction required. The attack complexity is high because the attacker must probe intermediary behavior and align request boundaries with the target deployment. Impact is limited to partial confidentiality and integrity effects; availability is not directly impacted. The EPSS probability for this CVE remains low, consistent with the specialized reconnaissance required.

Root Cause

The root cause is inconsistent interpretation of HTTP request framing headers between WebSphere's HTTP layer and upstream intermediaries. When both Content-Length and Transfer-Encoding: chunked are present, or when malformed chunked encoding is submitted, WebSphere may parse the request boundary differently than the fronting proxy. This mismatch is the defining condition of [CWE-444].

Attack Vector

An unauthenticated remote attacker sends specifically crafted HTTP requests containing ambiguous framing headers to a WebSphere endpoint reachable through a reverse proxy or load balancer. The proxy forwards what it treats as a single request while WebSphere parses two. The trailing bytes become a prefix of the next queued request from a legitimate user, enabling request hijacking, response queue poisoning, or authentication context reuse.

No verified proof-of-concept exploit code is publicly available for CVE-2026-11722. Technical details are described in the IBM Support Page for Node 7287740.

Detection Methods for CVE-2026-11722

Indicators of Compromise

HTTP requests containing both Content-Length and Transfer-Encoding headers arriving at WebSphere endpoints
Malformed chunked encoding, oversized chunk sizes, or unexpected whitespace and line terminators inside header values
Unexpected HTTP methods or paths appearing in application logs that do not correlate to legitimate client sessions
Session or authentication tokens being reused across mismatched source addresses within short windows

Detection Strategies

Enable strict HTTP parsing and request-smuggling detection modes on upstream proxies, load balancers, and web application firewalls
Compare front-end proxy access logs against WebSphere access logs and alert on divergent request counts or boundaries
Deploy signatures for known request-smuggling payloads (TE.CL, CL.TE, TE.TE variants) at the network perimeter
Correlate spikes in HTTP 400 and 501 responses from WebSphere with upstream 200 responses to identify parser desynchronization

Monitoring Recommendations

Forward WebSphere HTTP access and error logs to a centralized SIEM or data lake for cross-source correlation
Alert on requests where header parsing outcomes differ between the reverse proxy and the origin server
Track sudden changes in session-to-source-IP mappings, which may indicate hijacked request queues
Monitor IBM's advisory channel for updates to the IBM Support Page for Node 7287740

How to Mitigate CVE-2026-11722

Immediate Actions Required

Review the IBM Support Page for Node 7287740 and identify affected WebSphere Application Server and Liberty versions in your environment
Apply the IBM-provided interim fix or fix pack as soon as maintenance windows permit
Configure upstream proxies to reject requests that contain both Content-Length and Transfer-Encoding headers
Inventory all internet-facing WebSphere deployments and confirm each is protected by a smuggling-aware intermediary

Patch Information

IBM has published remediation guidance on the IBM Support Page for Node 7287740. Administrators should consult that advisory for the specific interim fixes, fix packs, and version numbers applicable to their WebSphere Application Server or WebSphere Application Server Liberty deployment. Apply fixes through IBM Fix Central using standard change control procedures.

Workarounds

Terminate HTTP connections at a smuggling-hardened reverse proxy and normalize headers before forwarding to WebSphere
Enforce HTTP/2 end-to-end where possible, which eliminates the ambiguous framing that enables classic smuggling techniques
Disable connection reuse (keep-alive) between the proxy and WebSphere so that queued requests cannot be poisoned
Deploy WAF rules that block requests with conflicting length indicators or malformed chunked encoding

bash

# Example WAF rule concept - block requests with both framing headers
# Adapt syntax to your specific WAF or proxy technology
SecRule REQUEST_HEADERS:Content-Length "@rx ." \
  "chain,deny,status:400,id:1011722,msg:'Potential HTTP Request Smuggling CVE-2026-11722'"
  SecRule REQUEST_HEADERS:Transfer-Encoding "@rx chunked"