Answer in brief
CVE-2026-4266 records a High severity (CVSS 8.4) vulnerability in WatchGuard Firebox Insecure Deserialization in Fireware Access Portal. The current sources do not mark it as known exploited. The current feed maps WatchGuard/Fireware OS (generic), WatchGuard/Fireware OS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.4. 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.
The current feed maps WatchGuard/Fireware OS (generic), WatchGuard/Fireware OS (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:watchguard:firebox_cloud:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m270:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m290:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m295:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m370:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m390:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m395:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m440:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m4600:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m470:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m4800:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m495:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m5600:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m570:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m5800:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m590:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m595:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m670:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m690:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_m695:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_nv5:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t115-w:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t125:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t125-w:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t145:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t145-w:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t185:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t20:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t25:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t40:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t45:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t55:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t70:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t80:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:firebox_t85:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:h:watchguard:fireboxv:-:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:watchguard:fireware:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| WatchGuard/Fireware OSgeneric | >=2025.1 <2026.2 || >=12.1 <12.12 | 2026.2, 12.12 |
| WatchGuard/Fireware OSgeneric | >=12.1 <12.11.9 | 12.11.9 |
Published upstream
Mar 30, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 10, 2026
An Insecure Deserialization vulnerability in WatchGuard Fireware OS allows an attacker that has obtained write access to the local filesystem through another vulnerability to execute arbitrary code in the context of the portald user. Note, this vulnerability does not affect Firebox platforms that do not support the Access Portal feature, including the T15 and T35.
Quoted source text, attributed separately from HOL analysis.