Security readout for executives and security teams
Plain-English summary
This Siemens vulnerability affects DNS handling in several building automation and embedded products. A malformed DNS response can crash affected systems or expose small amounts of memory. It is not listed in CISA KEV, and the source bundle does not show active exploitation.
Executive priority
Treat as a moderate operational resilience issue for building automation and embedded environments. Prioritize sites where affected devices rely on untrusted or weakly controlled network DNS paths, then schedule vendor-supported upgrades through normal change control.
Technical view
The flaw is an out-of-bounds read in DNS response parsing caused by insufficient validation of record lengths and counts. A network-positioned attacker could trigger denial of service or memory disclosure. Affected products include listed APOGEE, TALON, Nucleus, and SIMOTICS versions.
Likely exposure
Exposure is most likely in organizations running affected Siemens building automation controllers, SIMOTICS CONNECT 400, or embedded products using affected Nucleus DNS modules. The attacker needs a privileged network position, so exposure depends heavily on DNS path control and network segmentation.
Exploitation context
The CVSS vector is network-based but high-complexity, with no privileges or user interaction required. CISA KEV status is false in the bundle. Siemens describes possible denial of service or memory leakage from malformed DNS responses, but no active exploitation is cited.
Researcher notes
Evidence is limited to CVE metadata and Siemens advisory references in the bundle. The described primitive is CWE-125 out-of-bounds read during DNS response parsing. Do not assume remote internet exploitability without confirming DNS exposure and product deployment details.
Mitigation direction
- Upgrade affected APOGEE/TALON BACnet controllers to V3.5.5 or later.
- Upgrade affected P2 Ethernet controllers to V2.8.20 or later.
- Upgrade Nucleus ReadyStart V3 to V2017.02.3 or later.
- Upgrade Nucleus ReadyStart V4 to V4.1.0 or later.
- Upgrade SIMOTICS CONNECT 400 to V0.5.0.0 or later.
- Review Siemens advisories for Nucleus NET and source-code DNS module guidance.
Validation and detection
- Inventory Siemens APOGEE, TALON, SIMOTICS, and Nucleus deployments.
- Compare installed firmware or source versions against the affected version ranges.
- Identify products using Nucleus DNS modules in embedded builds.
- Confirm DNS traffic paths are limited to expected trusted infrastructure.
- Check Siemens advisories for product-specific update status and constraints.
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-125: 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-2020-27737 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
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H/E:P/RL:O/RC:C
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:U/C:L/I:N/A:H/E:P/RL:O/RC:C2.24.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H/E:P/RL:O/RC:C
Source materials
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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.