NVD / CVE Program· CNA WatchGuard

CVE-2026-4266: WatchGuard Firebox Insecure Deserialization in Fireware Access Portal

Noroxi assessment

Priority: Monitor (action score 33/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.27% (FIRST EPSS).
Someone with local access to the system can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 8.4 · v4.0—No exploit No fix recorded

Published: Mar 30, 2026
Updated: Aug 27, 2026
EPSS: 0.2% · 20th percentile
CWE: CWE-502

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 33 / 40 · 8.4 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · WatchGuard: 8.4; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
watchguard	fireware	cpe:2.3:o:watchguard:fireware
watchguard	firebox m295	cpe:2.3:h:watchguard:firebox_m295
watchguard	firebox m395	cpe:2.3:h:watchguard:firebox_m395
watchguard	firebox m495	cpe:2.3:h:watchguard:firebox_m495
watchguard	firebox m595	cpe:2.3:h:watchguard:firebox_m595
watchguard	firebox m695	cpe:2.3:h:watchguard:firebox_m695
watchguard	firebox t115-w	cpe:2.3:h:watchguard:firebox_t115-w
watchguard	firebox t125	cpe:2.3:h:watchguard:firebox_t125
watchguard	firebox t125-w	cpe:2.3:h:watchguard:firebox_t125-w
watchguard	firebox t145	cpe:2.3:h:watchguard:firebox_t145
watchguard	firebox t145-w	cpe:2.3:h:watchguard:firebox_t145-w
watchguard	firebox t185	cpe:2.3:h:watchguard:firebox_t185

and 25 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

watchguard fireware2025.1 and later · before 2026.2
watchguard fireware12.1 and later · before 12.12

Versions reported by the vendor

Affected version ranges reported by the assigning authority (WatchGuard). Independent of NVD's CPE analysis and usually ahead of it.

WatchGuard Fireware OS
- 2025.1 and later · before 2026.2affected
- 12.1 and later · before 12.12affected
- 12.1 and later · before 12.11.9affected

Same product

watchguard: all records

Other highest-scoring records for the same primary product.

CVE-2025-9242WatchGuard Firebox iked Out of Bounds Write VulnerabilityKEV
95Now
CVE-2022-26318On WatchGuard Firebox and XTM appliances, an unauthenticated user can execute arbitrary code, aka FBX-22786.KEV
92Now
CVE-2025-14733WatchGuard Firebox iked Out of Bounds Write VulnerabilityKEV
76This week

Published before and after this one in the same product

← EarlierCVE-2026-3343Mar 3, 2026 · WatchGuard Firebox Reflected Cross-Site-Scripting (XSS) Vulnerability in Fireware Web UI
20Monitor
← EarlierCVE-2026-3344Mar 3, 2026 · WatchGuard Firebox System Integrity Check Bypass
27Monitor
Later →CVE-2026-4315Mar 30, 2026 · WatchGuard Firebox Cross-Site Request Forgery (CSRF) in Fireware Web UI
28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

btaolfinder

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-13046184 days apartFireware OS Deserialization of Untrusted Data in samld Allows Remote Code Execution
30Monitor
CVE-2026-1337195 days apartWatchGuard Firebox Management Web UI Denial of Service via Unsafe Deserialization
27Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone with local access to the system can trigger it.
Administrator privileges are required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Local
Attack complexity: Low
Privileges required: High
User interaction: None
Scope: X

Weakness class (CWE)

CWE-502 · Deserialization of Untrusted Data

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

Data received over the network is deserialized into the language’s native object format without verifying its source. Code paths inside the object can be triggered during deserialization.

The bug in code

The whole CWE-502 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

python

1payload = sock.recv(65536)
2job = pickle.loads(payload)

Fixed

python

1payload = sock.recv(65536)
2if not hmac.compare_digest(sign(payload), header_sig):
3    raise PermissionError("invalid signature")
4job = JobSchema.validate(json.loads(payload))

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

Object InjectionCAPEC-586likelihood: Medium · High

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

psirt.watchguard.com/CVE-2026-4266

Show all references (1 more)

www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00007

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records