CVE-2026-73117Apache Juneau HTTP response splitting
CVE-2026-73117 is a HTTP response splitting in Apache Juneau, rated critical (10.0 on CVSS 4.0).
Why this priority: Critical, and reachable over the network without an account.
Published · Updated · NVD status: Deferred
What it is
Line breaks in input let an attacker add headers or a second response.
How it is reached
An attacker can exploit it over the network, without an account, and nobody has to click anything.
What an attacker gains
A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker smuggle requests past the proxy's checks. The damage can spread past the vulnerable component into others.
Is it being exploited?
There is no public report of exploitation yet. It can be exploited automatically, at scale. EPSS estimates a 0.44% chance of exploitation activity in the next 30 days, higher than 39% of scored CVEs.
What to do
- Upgrade Apache Juneau to 9.2.1 or later.
- Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
Description from NVD
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability in Apache Juneau.
The Apache Juneau REST server passed response header values and redirect targets to the servlet container unchecked. An application that sets a response header or redirect target from request data could let a remote client inject header lines (where the servlet container does not itself reject CR/LF) or redirect users to an arbitrary external site. The framework itself does not build headers or redirects from request data; exposure depends on application code.
This issue affects Apache Juneau: through 9.2.0.
Users are recommended to upgrade to version 9.2.1, which fixes the issue. Header values are now sanitized by default; applications that build redirect targets from request data must also switch from sendRedirect() to the new sendSafeRedirect().
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Proxies, load balancers and the servers behind them. The flaw sits between a front-end proxy and its back end.
Trust boundaries in play
- Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
- Isolation between components. The impact crosses out of the vulnerable component into others it should be isolated from.
- Between a front-end proxy and its back end. An attacker who crosses it can smuggle requests past the proxy's checks.
Questions to answer about your own systems
- Where does Apache Juneau run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.