Security readout for executives and security teams
Plain-English summary
Some Gallagher Android mobile clients may trust the wrong cloud certificate chain, letting a well-positioned attacker impersonate the legitimate Command Centre Server. That could expose or alter sensitive security-control communications. The issue is critical because confidentiality, integrity, and availability can all be impacted, although exploitation requires a man-in-the-middle position and is rated high complexity.
Executive priority
Treat this as a priority remediation item for organizations using Gallagher mobile access workflows. It affects a security platform client and can enable server impersonation, but urgency should be driven by confirmed Android client presence and network exposure rather than assumed active exploitation.
Technical view
CVE-2021-23155 is CWE-296 improper certificate chain validation in Gallagher Command Centre Mobile Client for Android. Affected versions include 8.60 before 8.60.065 and 8.50 and earlier. The CVSS 3.1 score is 9.0 with network attack vector, high attack complexity, no privileges, no user interaction, changed scope, and high CIA impact.
Likely exposure
Exposure is most likely where organizations still use Gallagher Command Centre Mobile Client for Android version 8.60 below 8.60.065, or 8.50 and earlier. Risk is higher for mobile users connecting over untrusted, shared, or attacker-influenced networks.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability requires a man-in-the-middle position to impersonate the legitimate Command Centre Server, which raises complexity but can be serious in physical security environments.
Researcher notes
The available evidence identifies product, affected version ranges, weakness class, and impact, but does not provide exploit details or active exploitation claims. Focus research on version validation, certificate-chain validation behavior, and whether any unsupported Android client deployments remain in production.
Mitigation direction
- Upgrade Android Mobile Client 8.60 installations to 8.60.065 or later.
- Remove or replace Android Mobile Client 8.50 and earlier where present.
- Check Gallagher’s advisory for supported fixed versions and deployment guidance.
- Restrict mobile client use on untrusted networks until fixed.
- Use MDM controls to block vulnerable client versions.
Validation and detection
- Inventory Android devices for Gallagher Command Centre Mobile Client installations.
- Verify installed app versions against 8.60.065 and affected 8.50-or-earlier ranges.
- Review MDM, app store, or endpoint records for unmanaged installs.
- Confirm vulnerable versions are upgraded, removed, or access-restricted.
- Document remaining exceptions and compensating controls.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-296: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-23155 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H2.26Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9CriticalVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://security.gallagher.com/Security-Advisories/CVE-2021-23155CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Following of a Certificate's Chain of Trust
Improper Following of a Certificate's Chain of Trust represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.