TCP Initial Sequence Number (ISN) prediction

Answer in brief

CVE-2026-88778 records a High severity (CVSS 8.8) vulnerability in TCP Initial Sequence Number (ISN) prediction. The current sources do not mark it as known exploited. The current feed maps Citrix NetScaler/ADC (generic), Citrix NetScaler/Gateway (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 27, 2026Updated Sep 27, 2026Source checked Sep 27, 2026First seen by HOL Sep 27, 2026Material review Sep 27, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.8
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Citrix NetScaler/ADC (generic), Citrix NetScaler/Gateway (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Citrix NetScaler/ADCgeneric	>=0 <14.1-73.37 \|\| >=0 <13.1-64.23 \|\| >=0 <14.1-73.37 FIPS \|\| >=0 <13.1.37.279 FIPS and NDcPP	14.1-73.37, 13.1-64.23, 14.1-73.37 FIPS, 13.1.37.279 FIPS and NDcPP, 13.1.37.279
Citrix NetScaler/Gatewaygeneric	>=0 <14.1-73.37 \|\| >=0 <13.1-64.23	14.1-73.37, 13.1-64.23

Recommended response

Check inventory. Check lockfiles and deployed manifests for Citrix NetScaler/ADC, Citrix NetScaler/Gateway.
Review the reported fix. Update Citrix NetScaler/ADC to 14.1-73.37; Citrix NetScaler/Gateway to 14.1-73.37 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 27, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 27, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 27, 2026

Sources and claim methodology

Source referencesupport.citrix.com

Upstream source description

Predictable exact value from previous values 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 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23.

Quoted source text, attributed separately from HOL analysis.