Security readout for executives and security teams
Plain-English summary
Certain SiHAS gateway/controller devices and the old SiHAS app lack account authentication and permission checks. An unauthorized nearby network user could control affected devices, creating confidentiality, integrity, and availability risk. The public bundle does not name a patch or confirm exploitation.
Executive priority
Treat this as a high-priority exposure review for sites using SiHAS building or control devices. Prioritize inventory, vendor guidance, and network restriction because unauthorized control could affect operations and safety-adjacent environments.
Technical view
CVE-2021-26637 is an improper authentication issue in SiHAS SGW-300, ACM-300, and GCM-300 firmware 1.xx and the old SiHAS app. CVSS 3.1 is 8.8 with adjacent-network attack vector, low complexity, no privileges, no user interaction, and high CIA impact.
Likely exposure
Exposure is most likely where affected SiHAS devices or the old app are still deployed and reachable from local, wireless, building, or operational networks. Internet exposure is not established by the provided CVSS vector or source bundle.
Exploitation context
No CISA KEV listing is provided, and the source bundle does not cite active exploitation. The risk is still material because the flaw removes authentication and authorization barriers for adjacent attackers.
Researcher notes
The public record is sparse. The affected scope is limited in the bundle to Shina System SiHAS firmware 1.xx and old app, specifically SGW-300, ACM-300, and GCM-300. Avoid assuming Internet exploitability or available patches without vendor evidence.
Mitigation direction
- Identify SGW-300, ACM-300, GCM-300, firmware 1.xx, and old SiHAS app deployments.
- Check Shina System and KRCERT guidance for supported updates or replacement advice.
- Remove or replace the old SiHAS app where still in use.
- Restrict device access to trusted management or local networks only.
- Monitor affected device networks for unauthorized control activity.
Validation and detection
- Inventory SiHAS model names and firmware versions against the affected list.
- Confirm whether the old SiHAS app remains installed or operational.
- Review network reachability from adjacent or shared network segments.
- Verify that vendor guidance has been checked and documented.
- Confirm compensating network restrictions are active around affected devices.
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-287: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. 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-2021-26637 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
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/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:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=66782CVE 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 Authentication
Improper Authentication represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.