Fireware OS Pre-Authentication Integer Overflow in Access Portal Allows Out-of-Bounds Write

published 2026-10-27 13 d ago modified 2026-11-04 4 d ago also EUVD-2026-111157

cvss: 9.2; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits: 0; none known

An integer overflow vulnerability in the WebSocket connection handling used by WatchGuard Fireware OS's Access Portal allows a remote, unauthenticated attacker to write beyond the bounds of a heap buffer by sending a specially crafted request while the Access Portal feature is enabled.

Patch / fix

fixed in 1

WatchGuard Fireware OS 12.5.22, 12.12.4, 2026.4

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 4 d ago (2026-11-04)

Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	9.2	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA	4.0	9.2	CVSS:4.0/AV:N/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

Affected products

WatchGuard Fireware OS

Classification

Weakness

CWE-190 Integer Overflow or Wraparound
CWE-288 Authentication Bypass Using an Alternate Path or Channel
CWE-787 Out-of-bounds Write

References

psirt.watchguard.com /CVE-2026-93866
vendor-advisory

Sources

CVE List CVE-2026-93866
NVD CVE-2026-93866

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary