Apache Juneau: Improper Neutralization of CRLF Sequences in HTTP Headers
CVE-2026-73117 is a critical-severity improper neutralization of CRLF sequences in HTTP headers vulnerability in Apache Juneau from Apache, with a CVSS 4.0 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 9.2.1 as the first without the flaw, so updating Apache Juneau to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.44% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Apache Juneau to 9.2.1 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Juneau | before 9.2.1 | 9.2.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- HighSerious loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- HighSerious loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- HighSerious loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (apache.org).
Official description
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().
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of CRLF Sequences in HTTP Headers
The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.
How developers prevent this class of flaw
- Construct HTTP headers very carefully, avoiding the use of non-validated input data.
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
More Improper Neutralization of CRLF Sequences in HTTP Headers vulnerabilities (CWE-113)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Apache Juneau
- 10.0 Critical severity
- 10.0 Critical severity
- 10.0 Critical severity
- 10.0 Critical severity
- 10.0 Critical severity
- 10.0 Critical severity
Recent Improper Neutralization of CRLF Sequences in HTTP Headers vulnerabilities
- 9.2 Critical severity
- 8.2 High severity
- 8.1 High severity
- 7.5 High severity
- 7.1 High severity
- 7.3 High severity
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