HOMEVULNERABILITIESCVE-2021-21266
MEDIUM

CVE-2021-21266

CWE-611Published: February 1, 2021· Updated: Jun 17, 2026

5.0
CVSS v3.1

Official Description

openHAB is a vendor and technology agnostic open source automation software for your home. In openHAB before versions 2.5.12 and 3.0.1 the XML external entity (XXE) attack allows attackers in the same network as the openHAB instance to retrieve internal information like the content of files from the file system. Responses to SSDP requests can be especially malicious. All add-ons that use SAX or JAXB parsing of externally received XML are potentially subject to this kind of attack. In openHAB, the following add-ons are potentially impacted: AvmFritz, BoseSoundtouch, DenonMarantz, DLinkSmarthome, Enigma2, FmiWeather, FSInternetRadio, Gce, Homematic, HPPrinter, IHC, Insteon, Onkyo, Roku, SamsungTV, Sonos, Roku, Tellstick, TR064, UPnPControl, Vitotronic, Wemo, YamahaReceiver and XPath Tranformation. The vulnerabilities have been fixed in versions 2.5.12 and 3.0.1 by a more strict configuration of the used XML parser.

NVD Source

Technical Analysis

CVE-2021-21266 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeChanged
Impact
ConfidentialityLow
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

Affected Vendors & Products

openhab1 product(s)
openhab
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/openhab/openhab-addons/commit/81935b0ab126e6d9aebd2f6c3fc67d82bb7e8b86
PATCHhttps://github.com/openhab/openhab-addons/security/advisories/GHSA-r2hc-pmr7-4c9r
PATCHhttps://github.com/openhab/openhab-addons/commit/81935b0ab126e6d9aebd2f6c3fc67d82bb7e8b86
PATCHhttps://github.com/openhab/openhab-addons/security/advisories/GHSA-r2hc-pmr7-4c9r
ADVISORYhttps://dev.to/brianverm/configure-your-java-xml-parsers-to-prevent-xxe-213c
ADVISORYhttps://www.contrastsecurity.com/security-influencers/xml-xxe-pitfalls-with-jaxb
ADVISORYhttps://dev.to/brianverm/configure-your-java-xml-parsers-to-prevent-xxe-213c
ADVISORYhttps://www.contrastsecurity.com/security-influencers/xml-xxe-pitfalls-with-jaxb

All References (8)

→
https://dev.to/brianverm/configure-your-java-xml-parsers-to-prevent-xxe-213cThird Party Advisory
→
https://github.com/openhab/openhab-addons/commit/81935b0ab126e6d9aebd2f6c3fc67d82bb7e8b86Patch · Third Party Advisory
→
https://github.com/openhab/openhab-addons/security/advisories/GHSA-r2hc-pmr7-4c9rPatch · Third Party Advisory
→
https://www.contrastsecurity.com/security-influencers/xml-xxe-pitfalls-with-jaxbTechnical Description · Third Party Advisory
→
https://dev.to/brianverm/configure-your-java-xml-parsers-to-prevent-xxe-213cThird Party Advisory
→
https://github.com/openhab/openhab-addons/commit/81935b0ab126e6d9aebd2f6c3fc67d82bb7e8b86Patch · Third Party Advisory
→
https://github.com/openhab/openhab-addons/security/advisories/GHSA-r2hc-pmr7-4c9rPatch · Third Party Advisory
→
https://www.contrastsecurity.com/security-influencers/xml-xxe-pitfalls-with-jaxbTechnical Description · Third Party Advisory

Quick Facts

CVE IDCVE-2021-21266
CVSS Score5.0 / 10
SeverityMEDIUM
WeaknessCWE-611
CISA KEVNo
Affected1 vendor(s)
PublishedFeb 1, 2021

Related CVEs (CWE-611)

CVE-2018-1000820
10.0
CVE-2018-1000652
10.0
CVE-2018-1000644
10.0
CVE-2017-8110
10.0
CVE-2018-1000651
10.0
CVE-2018-1000821
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21266 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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