Security Bulletin
Summary
react-router is used by IBM Optim as part of its front-end user interface (Optim UI) to provide client-side and server-side routing for the web application. CVE-2026-33244 and CVE-2026-33245 are cross-site scripting (XSS) vulnerabilities in react-router's redirect and RSC handling; CVE-2026-34077 is a denial of service vulnerability via reflected user input in single-fetch; CVE-2026-40181 is an open redirect vulnerability via protocol-relative URL reinterpretation; CVE-2026-42211 is a potential remote code execution vulnerability exploitable via a two-step attack chained onto prototype pollution; and CVE-2026-42342 is a denial of service vulnerability via unbounded path expansion in the __manifest endpoint. IBM Optim 2.0.0 resolves all listed vulnerabilities.
Vulnerability Details
CVEID: CVE-2026-33244
DESCRIPTION: React Router is a router for React. In versions 7.5.1 through 7.13.1, when using Framework Mode with pre-rendering enabled, improper neutralization of the HTTP `Location` header value can permit Cross-Site Scripting (XSS) in the statically generated HTML files if the redirect location comes from an untrusted source. This does not impact applications using Declarative Mode (`BrowserRouter`) or Data Mode (`createBrowserRouter/RouterProvider`). This is patched in version 7.13.2.
CWE: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVSS Source: security-advisories@github.com
CVSS Base score: 5.4
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N)
CVEID: CVE-2026-33245
DESCRIPTION: React Router is a router for React. In versions 7.7.0 through 7.13.1, when using React Router's unstable React Server Components (RSC) APIs, there is a potential client-side Cross-Site Scripting (XSS) vulnerability in the RSC redirect handling if redirects come from untrusted sources. This does not impact applications that are not using the unstable RSC APIs in React Router. This is patched in version 7.13.2.
CWE: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVSS Source: NVD
CVSS Base score: 4.7
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N)
CVEID: CVE-2026-34077
DESCRIPTION: React Router is a router for React. In versions 7.7.0 through 7.13.1, when using React Router's unstable React Server Components (RSC) APIs, there is a potential client-side Cross-Site Scripting (XSS) vulnerability in the RSC redirect handling if redirects come from untrusted sources. This does not impact applications that are not using the unstable RSC APIs in React Router. This is patched in version 7.13.2.
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
CVSS Source: security-advisories@github.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVEID: CVE-2026-40181
DESCRIPTION: React Router is a router for React. In versions 7.0.0 through 7.14.0 and 6.7.0 through 6.30.3, certain URLs passed to the redirect function can trigger an open redirect to an external domain due to path values starting with // being reinterpreted as protocol-relative URLs. The level of impact depends on the validation done by the application prior to returning the redirect. This does not impact applications using Declarative Mode (BrowserRouter). This is patched in versions 7.14.1 and 6.30.4.
CWE: CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
CVSS Source: NVD
CVSS Base score: 6.1
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
CVEID: CVE-2026-42211
DESCRIPTION: React Router is a router for React. In versions 7.0.0 through 7.14.1, when using Framework Mode, a combination of steps could potentially allow unauthorized remote code execution (RCE) through external requests. This attack requires the application code to have an existing prototype pollution vulnerability, which can then be leveraged in a 2-step attack where the second step triggers unauthorized RCE on the remote server. This does not impact applications using Declarative Mode (`BrowserRouter`) or Data Mode (`createBrowserRouter/RouterProvider`). This is patched in version 7.14.2.
CWE: CWE-502: Deserialization of Untrusted Data
CVSS Source: security-advisories@github.com
CVSS Base score: 8.1
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)
CVEID: CVE-2026-42342
DESCRIPTION: React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (`BrowserRouter`) or Data Mode (`createBrowserRouter/RouterProvider`). This is patched in react-router version 7.15.0 and @remix-run/server-runtime version 2.17.5.
CWE: CWE-400: Uncontrolled Resource Consumption
CVSS Source: security-advisories@github.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM Optim | 1.0.0 |
| IBM Optim | 1.1.0 |
| IBM Optim | 1.2.0 |
Remediation/Fixes
Move to IBM Optim 2.0.0, which resolves all vulnerabilities listed in this bulletin. The following package has been upgraded from its vulnerable version to the patched version:
react-router — upgraded from 7.7.0 (Optim 1.0.0, 1.1.0) / 7.12.0 (Optim 1.2.0) → 7.18.1, resolving CVE-2026-33244, CVE-2026-33245, CVE-2026-34077, CVE-2026-40181, CVE-2026-42211, and CVE-2026-42342.
Available from https://www.ibm.com/software/passportadvantage/pao-customer
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
CVE-2026-33244 — National Vulnerability Database
CVE-2026-33245 — National Vulnerability Database
CVE-2026-34077 — National Vulnerability Database
CVE-2026-40181 — National Vulnerability Database
CVE-2026-42211 — National Vulnerability Database
CVE-2026-42342 — National Vulnerability Database
Acknowledgement
Change History
21 Sep 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
21 September 2026
Initial Publish date:
21 September 2026
UID
ibm17288695