CyberSecBulletin
CVE-2026-116606Exploited in the wildNVD status: Analyzed

Barracuda Networks Email Security Gateway (ESG) Authentication Bypass Using an Alternate Path or Channel

Published Updated By the CyberSecBulletin desk

CVE-2026-116606 is a critical-severity authentication bypass using an alternate path or channel vulnerability in Barracuda Email Security Gateway (ESG) from Barracuda Networks, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 9.4.0.030 as the first without the flaw, so updating Barracuda Email Security Gateway (ESG) to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 10, 2026, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Barracuda Email Security Gateway (ESG) to 9.4.0.030 or a later version.
  2. Update Email Security Gateway 300 Firmware to 9.4.0.030 or a later version.
  3. Update Email Security Gateway 400 Firmware to 9.4.0.030 or a later version.
  4. CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
  5. Read the advisory on trust.barracuda.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Barracuda NetworksBarracuda Email Security Gateway (ESG)before 9.4.0.0309.4.0.030
BarracudaEmail Security Gateway 300 Firmwarebefore 9.4.0.0309.4.0.030
BarracudaEmail Security Gateway 400 Firmwarebefore 9.4.0.0309.4.0.030
BarracudaEmail Security Gateway 600 Firmwarebefore 9.4.0.0309.4.0.030
BarracudaEmail Security Gateway 800 Firmwarebefore 9.4.0.0309.4.0.030
BarracudaEmail Security Gateway 900 Firmwarebefore 9.4.0.0309.4.0.030

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.09.3CriticalCNA (google.com)
CVSS 3.19.8CriticalNVD

Official description

An authentication bypass in Barracuda Email Security Gateway versions earlier than 9.4.0.030 allows an unauthenticated remote attacker to invoke a configuration-import function and restore a crafted, compatible backup archive, resulting in unauthorized modification of the appliance’s global configuration.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Authentication Bypass Using an Alternate Path or Channel

The product requires authentication, but the product has an alternate path or channel that does not require authentication.

How developers prevent this class of flaw

  • Funnel all access through a single choke point to simplify how users can access a resource. For every access, perform a check to determine if the user has permissions to access the resource.

More Authentication Bypass Using an Alternate Path or Channel vulnerabilities (CWE-288)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Record last changed materially (score, affected products, status or references).
  5. Deadline for US federal agencies to remediate, set by CISA.

References

Our coverage

Other vulnerabilities in Barracuda Email Security Gateway (ESG)

All Barracuda Email Security Gateway (ESG) vulnerabilities

Recent Authentication Bypass Using an Alternate Path or Channel vulnerabilities

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