Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:A) | Adjacent network |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:P) | Attack requirements present |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:H) | High confidentiality impact |
| Integrity (VI:H) | High integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:A/AC:L/AT:P/PR:N/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
About Watchguard Fireware
CVE-2026-8247 affects Watchguard Fireware, a product from Watchguard. Before acting, confirm where Watchguard Fireware runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: An Out-of-bounds Write vulnerability in WatchGuard Fireware OS may allow an unauthenticated attacker on the same local network segment to execute arbitrary code. This vulnerability affects Fireware OS 11.0 up to and including 11.12.4_Update1, 12.0 up to and including 12.12 and 2025.1 up to and including 2026.2.
The weakness class is Classic Buffer Overflow. Data is copied into a buffer without checking its size.
Based on its CVSS vector, the flaw needs local or adjacent access, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Watchguard Fireware |
| Affected versions | Fireware from 11.0.0 before 11.12.4; Fireware 11.12.4; Fireware from 12.5 before 12.5.19; Fireware from 2025.1 before 2026.2.1; Fireware from 12.0 before 12.12.1 |
| Published | Jul 3, 2026 |
| Last modified | Aug 28, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | 5d1c2695-1a31-4499-88ae-e847036fd7e3 |
How to detect it
- Inventory every instance of Watchguard Fireware and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Watchguard Fireware named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Watchguard Fireware to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-120: Classic Buffer Overflow More CVEs with this weakness
- CWE-787: Out of Bounds Write More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
A NULL pointer dereference vulnerability in the WatchGuard Fireware OS authentication process allows a remote, unauthenticated attacker to crash the management daemon by sending a specially request to the login interface, resulting in a denial of service.
A missing authorization vulnerability in the wgagent management daemon's session initialization function allows an authenticated, low-privileged user (including a read-only or guest administrator account) to crash the wgagent process and read arbitrary files accessible to the daemon by submitting a specially crafted management API request.
A missing authorization vulnerability in the wgagent management daemon's session initialization function allows an authenticated, low-privileged user (including a read-only or guest administrator account) to crash the wgagent process and read arbitrary files accessible to the daemon by submitting a specially crafted management API request.
An integer underflow vulnerability in the WatchGuard Fireware OS IKE daemon (iked) allows a remote attacker who has completed the initial IKEv2 handshake to crash the iked process by sending a specially crafted encrypted IKEv2 message, resulting in a denial of service.
An integer underflow vulnerability in the WatchGuard Fireware OS IKEv2 daemon (iked) allows a remote, unauthenticated attacker to crash the process by sending a specially crafted encrypted IKEv2 message negotiated with an AES-GCM cipher suite.
A code injection vulnerability in WatchGuard Fireware OS's BOVPN Over TLS client configuration handling allows an attacker who controls the remote VPN server to execute arbitrary commands as root on the connecting Firebox.
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