ADC: Inconsistent Interpretation of HTTP Requests
CVE-2026-88773 is a critical-severity inconsistent interpretation of HTTP requests vulnerability in ADC from Citrix NetScaler, with a CVSS 3.1 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 versions 14.1-73.37, 13.1-64.23, 14.1-73.37 FIPS as the first without the flaw, so updating ADC to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 3.08% chance of exploitation within 30 days, higher than 88% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update ADC to 14.1-73.37 or 13.1-64.23 or 14.1-73.37 FIPS or 13.1-37.279 and NDcPP, whichever matches your release line, or a later version.
- Update Gateway to 14.1-73.37 FIPS or 13.1-64.23, whichever matches your release line, or a later version.
- Update Netscaler Application Delivery Controller to 13.1-64.23 or 13.1.37.279 or 14.1-73.37, whichever matches your release line, or a later version.
- Read the advisory on support.citrix.com for workarounds and exact fixed builds.
- 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 |
|---|---|---|---|
| Citrix NetScaler | ADC | before 14.1-73.37; before 13.1-64.23; before 14.1-73.37 FIPS; before 13.1-37.279 and NDcPP | 14.1-73.37, 13.1-64.23, 14.1-73.37 FIPS, 13.1-37.279 and NDcPP |
| Citrix NetScaler | Gateway | before 14.1-73.37 FIPS; before 13.1-64.23 | 14.1-73.37 FIPS, 13.1-64.23 |
| Citrix | Netscaler Application Delivery Controller | 13.1 up to, but not including, 13.1-64.23; 13.1 up to, but not including, 13.1.37.279; 14.1 up to, but not including, 14.1-73.37; 14.1-66.68 through 14.1-73.37 | 13.1-64.23, 13.1.37.279, 14.1-73.37 |
| Citrix | Netscaler Gateway | 13.1 up to, but not including, 13.1-64.23; 14.1 up to, but not including, 14.1-73.37 | 13.1-64.23, 14.1-73.37 |
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.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA |
| CVSS 3.1 | 10.0 | Critical | NVD |
Official description
Inconsistent interpretation of HTTP requests ('HTTP Request/Response smuggling') vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1-37.279 and NDcPP; Gateway: before 14.1-73.37 FIPS and before 13.1-64.23.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inconsistent Interpretation of HTTP Requests
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How developers prevent this class of flaw
- Use a web server that employs a strict HTTP parsing procedure, such as Apache.
- Terminate the client session after each request.
More Inconsistent Interpretation of HTTP Requests vulnerabilities (CWE-444)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in ADC
- 7.5 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.2 High severity
- 8.1 High severity
Recent Inconsistent Interpretation of HTTP Requests vulnerabilities
- 7.3 High severity
- 9.1 Critical severity
- 7.5 High severity
- 8.2 High severity
- 9.8 Critical severity
- 8.7 High severity
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