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No exploitation reportedFix available

CVE-2020-27736

No exploitation reported by the sources we read.

  • Published2021-04-22
  • WeaknessCWE-125 · CWE-170

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20), APOGEE PXC Modular (BACnet) (All versions < V3.5.5), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.3), Nucleus ReadyStart V4 (All versions < V4.1.0), Nucleus Source Code (Versions including affected DNS modules), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), TALON TC Compact (BACnet) (All versions < V3.5.5), TALON TC Modular (BACnet) (All versions < V3.5.5). The DNS domain name label parsing functionality does not properly validate the null-terminated name in DNS-responses. The parsing of malformed responses could result in a read past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition or leak the read memory.

Timeline

dates in UTC
  1. 2021-04-2221:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-27736?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-27736?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Siemens nucleus net
BranchAffectedFixed in
—all versionsno fix published
Siemens nucleus readystart v3
BranchAffectedFixed in
2017.2< 2017.02.32017.02.3
Siemens nucleus readystart v4
BranchAffectedFixed in
4.1< 4.1.04.1.0

2 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • ICSA-22-349-16 CISA6 known affected

    Siemens APOGEE and TALON

    APOGEE PXC Compact (BACnet) · APOGEE PXC Compact (P2 Ethernet) · APOGEE PXC Modular (BACnet) · +3 more

  • ICSA-21-103-13 CISA1 known affected

    Siemens SIMOTICS CONNECT 400 (Update A)

    SIMOTICS CONNECT 400

Full record on NVD

Fix

  1. Vendor fix CISA ICSA-22-349-16 · 2 productsUpdate to V2.8.20 or later version
  2. Vendor fix CISA ICSA-22-349-16 · 4 productsUpdate to V3.5.5 or later version
  3. Vendor fix CISA ICSA-21-103-13 · 1 productUpdate to V0.5.0.0 or later version

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CNACVSS 3.16.5read 2026-10-23
  • NVDCVSS 3.16.5read 2026-10-23
  • NVDCVSS 2.05.8read 2026-10-23
  • CNAweakness (CWE)CWE-170read 2026-10-23
  • NVDweakness (CWE)CWE-125read 2026-10-23
  • FIRST EPSSEPSS score3.6 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
Published
2021-04-22
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2020-27736?

A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20), APOGEE PXC Modular (BACnet) (All versions < V3.5.5), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.3), Nucleus ReadyStart V4 (All versions < V4.1.0), Nucleus Source Code (Versions including affected DNS modules), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), TALON TC Compact (BACnet) (All versions < V3.5.5), TALON TC Modular (BACnet) (All versions < V3.5.5). The DNS domain name label parsing functionality does not properly validate the null-terminated name in DNS-responses. The parsing of malformed responses could result in a read past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition or leak the read memory.

Is CVE-2020-27736 actively exploited?

Active exploitation of CVE-2020-27736 has not been confirmed. Its EPSS score was 3.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-27736?

CVE-2020-27736 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H.

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