Is CVE-2026-103593 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-103593 being exploited in the wild.

How severe is CVE-2026-103593?

Informational severity, published 27 October 2026.

Which products and versions are affected?

Watchguard Fireware OS Default versions < 2026.4 and < 12.12.4; T15/T35 < 12.5.22.

How is CVE-2026-103593 attacked?

It is attacked over the network or from the adjacent network, in a network appliance.

Am I affected by CVE-2026-103593?

Check whether you run Watchguard Fireware OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-103593: WatchGuard Fireware OS stack buffer overflow in logging service

Q: Is there a fix for CVE-2026-103593?

Yes: fixed in Fireware OS 2026.4, Fireware OS 12.12.4, Fireware OS 12.5.22. Until then: This vulnerability only affects Firebox deployments in FIPS mode with an external log server configured; deployments without external logging or not in FIPS mode are not affected. [{"kind": "disclosed", "at": "2026-10-27"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

CVE-2026-103593 · Severity: info · Published 2026-10-27

WatchGuard Fireware OS is the operating system for Firebox network security appliances that protect corporate networks. A stack buffer overflow in the logging service allows a network-adjacent attacker to execute arbitrary code with root privileges if they can intercept traffic to an external log server and present a specially crafted certificate. This could give an attacker complete control over the firewall and access to all traffic passing through it.

Technologies: Watchguard Fireware OS. Vendors: Watchguard.

Quick answers

Is CVE-2026-103593 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-103593 being exploited in the wild.
How severe is CVE-2026-103593?: Informational severity, published 27 October 2026.
Which products and versions are affected?: Watchguard Fireware OS Default versions < 2026.4 and < 12.12.4; T15/T35 < 12.5.22.
Is there a fix for CVE-2026-103593?: Yes: fixed in Fireware OS 2026.4, Fireware OS 12.12.4, Fireware OS 12.5.22. Until then: This vulnerability only affects Firebox deployments in FIPS mode with an external log server configured; deployments without external logging or not in FIPS mode are not affected.</anigation> <parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-27"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-103593 attacked?: It is attacked over the network or from the adjacent network, in a network appliance.
Am I affected by CVE-2026-103593?: Check whether you run Watchguard Fireware OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: Fireware OS 2026.4, Fireware OS 12.12.4, Fireware OS 12.5.22

This vulnerability only affects Firebox deployments in FIPS mode with an external log server configured; deployments without external logging or not in FIPS mode are not affected.</anigation> <parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-27"}]

Technical details

A stack-based buffer overflow (CWE-121) in the Fireware OS logging service is triggered by a specially crafted certificate presented during communication with an external log server. The vulnerability requires network adjacency and the ability to impersonate or intercept traffic to the configured log server, and only affects Firebox deployments running in FIPS mode with an external log server configured. Successful exploitation grants arbitrary code execution with root privileges.

Affected products

WatchGuard Fireware OS Default versions < 2026.4 and < 12.12.4; T15/T35 < 12.5.22

References

https://psirt.watchguard.com/CVE-2026-103593

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