# What is CVE-2026-28369? > CVE-2026-28369 is a critical-severity flaw (CVSS 9.1) in Undertow from Red Hat, published on 27 March 2026. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 0.9%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2026-28369 ## At a glance - **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. - **Precursor Intelligence risk score:** 54 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes. - **Severity:** Critical (CVSS 9.1 out of 10) - **Known to be exploited:** No, not on the list of flaws known to be exploited today - **Chance of use in the next 30 days:** 0.9% (latest exploit-likelihood forecast) - **Published:** 27 March 2026 - **Record last updated:** 21 September 2026 - **Main product:** Undertow from Red Hat - **Affected products:** 10 ## What is CVE-2026-28369? In plain terms It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data and change data. ### The official description A flaw was found in Undertow. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploited by a remote attacker to perform request smuggling. Request smuggling allows an attacker to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or data exposure. ### What kind of flaw is it? - CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') ### How an attack on it works - Where an attacker can be: Anywhere on the internet - How hard it is to pull off: Easy: no special conditions - Login needed first: No login needed - Does someone have to click: No, nobody has to do anything - What an attacker gets: Can read data and change data Severity vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N` ## Is CVE-2026-28369 being exploited? Not that we know of It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.9%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 0.9%, 0.9%, 0.9%, 0.9%, 0.9%, 0.9%, 0.9%. ### Timeline - 27 March 2026: Published - 21 September 2026: Record last updated ### How Precursor Intelligence ranks it CVE-2026-28369 scores **54 out of 100 (Medium)**, with the action "Plan remediation". Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less: - Evidence it is being exploited: biggest factor - How severe it is: strong factor - How widely exposed it is: smaller factor - Threat activity around it: smaller factor 85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it. ## Who is affected by CVE-2026-28369? The published record lists 10 products. - [Undertow](https://www.precursorintelligence.com/product/redhat/undertow) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): version not specified - [Jboss Enterprise Application Platform](https://www.precursorintelligence.com/product/redhat/jboss_enterprise_application_platform) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 7.0.0, 8.0.0 - [Build of Apache Camel - Hawtio](https://www.precursorintelligence.com/product/redhat/build_of_apache_camel_-_hawtio) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 4.0 - [Build of Apache Camel for Spring Boot](https://www.precursorintelligence.com/product/redhat/build_of_apache_camel_for_spring_boot) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 4.0 - [Data Grid](https://www.precursorintelligence.com/product/redhat/data_grid) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 8.0 - [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.0 - [Fuse](https://www.precursorintelligence.com/product/redhat/fuse) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 7.0.0 - [Jboss Enterprise Application Platform Expansion Pack](https://www.precursorintelligence.com/product/redhat/jboss_enterprise_application_platform_expansion_pack) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): version not specified - [Process Automation](https://www.precursorintelligence.com/product/redhat/process_automation) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 7.0 - [Single Sign-on](https://www.precursorintelligence.com/product/redhat/single_sign-on) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 7.0 ## How do I fix CVE-2026-28369? 1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list. 2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list. 3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in. 4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood. ### References - [access.redhat.com](https://access.redhat.com/security/cve/CVE-2026-28369) (Vendor advisory) - [bugzilla.redhat.com](https://bugzilla.redhat.com/show_bug.cgi?id=2443262) (Issue tracking, Vendor advisory) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:25125) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:25126) ## Questions ### What is CVE-2026-28369? CVE-2026-28369 is a critical-severity flaw in Undertow from Red Hat, published on 27 March 2026. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data and change data. ### How serious is CVE-2026-28369? It scores 9.1 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2026-28369 is 54 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month. ### Is CVE-2026-28369 being exploited? It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.9%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2026-28369 affect? For Undertow from Red Hat: version not specified. The record lists 10 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2026-28369? Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. ## Does CVE-2026-28369 affect you? Precursor Intelligence keeps checking for you: - **Tell us what you run.** Pick your software from a list, or let us work it out from your website. - **We match it to every flaw.** Over 400,000 published flaws, checked against your list. - **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it. - **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools. Start free (no card, nothing to install): https://www.precursorintelligence.com/register Book a demo: https://www.precursorintelligence.com/contact