ADC: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-8655 is a critical-severity improper restriction of operations within the bounds of a memory buffer vulnerability in ADC from NetScaler, 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 72.61, 63.18, 37.272 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 0.63% chance of exploitation within 30 days, higher than 51% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update ADC to 72.61 or 63.18 or 37.272, whichever matches your release line, or a later version.
- Update Gateway to 72.61 or 63.18, whichever matches your release line, or a later version.
- Update Netscaler Application Delivery Controller to 13.1-37.272 or 13.1-63.18 or 14.1-72.61, 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 |
|---|---|---|---|
| NetScaler | ADC | 14.1 up to, but not including, 72.61; 13.1 up to, but not including, 63.18; 14.1 FIPS up to, but not including, 72.61; 13.1 FIPS and NDcPP up to, but not including, 37.272 | 72.61, 63.18, 37.272 |
| NetScaler | Gateway | 14.1 up to, but not including, 72.61; 13.1 up to, but not including, 63.18 | 72.61, 63.18 |
| Citrix | Netscaler Application Delivery Controller | before 13.1-37.272; 13.1 up to, but not including, 13.1-63.18; 14.1 up to, but not including, 14.1-72.61; 14.1-66.68 | 13.1-37.272, 13.1-63.18, 14.1-72.61 |
| Citrix | Netscaler Gateway | 13.1 up to, but not including, 13.1-63.18; 14.1 up to, but not including, 14.1-72.61 | 13.1-63.18, 14.1-72.61 |
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 4.0 | 8.8 | High | CNA |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
Multiple Memory overflow vulnerabilities in NetScaler ADC and NetScaler Gateway leading to unpredictable or erroneous behavior and Denial of Service if NetScaler ADC is configured as an LB of type Oracle OR NetScaler ADC is configured as a DNS Proxy OR NetScaler ADC is configured as a DNS recursive resolver deployment
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of Operations within the Bounds of a Memory Buffer
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
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
- 9.5 Critical severity
- 7.5 High severity
- 9.8 Critical severity
- 8.8 High severity
- 9.8 Critical severity
- 7.5 High severity
Recent Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerabilities
- 7.3 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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