Citrix NetScaler ADC and NetScaler Gateway Code Injection
CVE-2023-3519 is a critical-severity improper control of generation of code vulnerability in NetScaler ADC from Citrix, with a CVSS 3.1 base score of 9.8 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 49.13, 91.13, 37.159 as the first without the flaw, so updating NetScaler ADC to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on July 19, 2023, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update NetScaler ADC to 49.13 or 91.13 or 37.159 or 55.297, whichever matches your release line, or a later version.
- Update NetScaler Gateway to 49.13 or 91.13, whichever matches your release line, or a later version.
- Update Netscaler Application Delivery Controller to 12.1-55.297 or 13.0-91.13 or 13.1-37.159 or 13.1-49.13, whichever matches your release line, or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- 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 | 13.1 up to, but not including, 49.13; 13.0 up to, but not including, 91.13; 13.1-FIPS up to, but not including, 37.159; 12.1-FIPS up to, but not including, 55.297; 12.1-NDcPP up to, but not including, 55.297 | 49.13, 91.13, 37.159, 55.297 |
| Citrix | NetScaler Gateway | 13.1 up to, but not including, 49.13; 13.0 up to, but not including, 91.13 | 49.13, 91.13 |
| Citrix | Netscaler Application Delivery Controller | 12.1 up to, but not including, 12.1-55.297; 13.0 up to, but not including, 13.0-91.13; 13.1 up to, but not including, 13.1-37.159; 13.1 up to, but not including, 13.1-49.13 | 12.1-55.297, 13.0-91.13, 13.1-37.159, 13.1-49.13 |
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
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA (citrix.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
Unauthenticated remote code execution
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-3519US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/173997/Citrix-ADC-NetScaler-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
Other vulnerabilities in NetScaler ADC
- 7.5 High severity
Recent Improper Control of Generation of Code vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 10.0 Critical severity
- 7.8 High severity
- 8.8 High severity
- 8.0 High severity
Spotted an error? Tell us.