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Websphere Application ServerApplication · Ibm

CVE-2026-11541

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-30
Fix available
A fix is available. Upgrade to 8.5.5.31 / 9.0.5.29 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
IBM CICS Transaction Gateway for Multiplatforms 9.1, 9.2, 9.3, and 10.1 IBM WebSphere Application Server 9.0, and 8.5 and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.6 are affected by an HTTP request smuggling vulnerability.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

IBM WebSphere Application Server 9.0, 8.5 and WebSphere Liberty 17.0.0.3 through 26.0.0.6 contain an HTTP request smuggling vulnerability that allows attackers to manipulate how HTTP requests are parsed by front-end and back-end servers, potentially bypassing security controls and gaining unauthorized access.

MitigationApply IBM security patches for CVE-2026-11541 when available. Review and align Content-Length and Transfer-Encoding header handling between front-end proxies and WebSphere to prevent request smuggling attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Websphere Application ServerApplication
Affected:>= 8.5.0.0, < 8.5.5.31>= 9.0.0.0, < 9.0.5.29>= 17.0.0.3, <= 26.0.0.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify WebSphere Application Server traditional edition version
    Check the version using the versionInfo.sh script in the bin directory: ./versionInfo.sh | grep -i version, or inspect the install_dir/properties/version/Version.info file
    Affected if The installed version is >= 8.5.0.0 and < 8.5.5.31, OR >= 9.0.0.0 and < 9.0.5.29
  2. Identify WebSphere Liberty version
    Check the version by inspecting the lib/versions/libVersions.xml file, or run: java -jar wlp/lib/versions/libVersions.xml, or check the server.xml for the version attribute
    Affected if The installed version is >= 17.0.0.3 and <= 26.0.0.6
  3. Determine if WebSphere is exposed behind a front-end proxy or load balancer
    Review network architecture and proxy configuration to identify if an upstream proxy (e.g., IHS, nginx, Apache, HAProxy) forwards requests to WebSphere
    Affected if A front-end proxy or load balancer is present and forwards requests to WebSphere, creating the parsing mismatch condition for HTTP request smuggling
  4. Inspect Content-Length and Transfer-Encoding header handling
    Review the server.xml configuration (for Liberty) or httpchannel plugin-cfg.xml (for traditional) for any explicit handling of these headers, and test by sending ambiguous requests with both headers present
    Affected if The server accepts and forwards requests containing both Content-Length and Transfer-Encoding headers without rejecting or normalizing them

A user is affected if their WebSphere version falls within the affected ranges AND the server is accessible through a front-end proxy or handles ambiguous HTTP request headers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.5.5.31 / 9.0.5.29 or later
Fixed in 8.5.5.319.0.5.29
Interim mitigation

Apply IBM security patches for CVE-2026-11541 when available. Review and align Content-Length and Transfer-Encoding header handling between front-end proxies and WebSphere to prevent request smuggling attempts.

Recommended fix Moderate confidence

WebSphere traditional 8.5.x -> 8.5.5.31+; WebSphere traditional 9.0.x -> 9.0.5.29+; WebSphere Liberty -> latest available fix pack (beyond 26.0.0.6)

  1. Identify the WebSphere edition in use (traditional or Liberty) by checking the installation directory and version info
  2. For WebSphere Application Server traditional 8.5.x: Upgrade to version 8.5.5.31 or later by applying the latest fix pack from IBM Fix Central
  3. For WebSphere Application Server traditional 9.0.x: Upgrade to version 9.0.5.29 or later by applying the latest fix pack from IBM Fix Central
  4. For WebSphere Liberty (17.0.0.3 through 26.0.0.6): Download and install the latest available Liberty fix pack from IBM Fix Central which addresses this vulnerability
  5. After upgrade, verify the new version matches or exceeds the minimum fixed version for your edition
  6. Test critical applications to ensure functionality is preserved after the update
Caveat Standard risk of compatibility issues with custom configurations or older Java versions - review IBM's migration guides before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Websphere Application Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-11541 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data