What’s Vulnerable › Vulnerabilities

CVE-2021-21266: XXE vulnerability in OpenHAB

• Severity: medium (CVSS 5.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-01 · updated 2026-06-17
• Weakness: CWE-611

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.

Affected products

• openhab-webui: before 2.5.12; 3.0.0 — fixed in 2.5.12

How to fix

Upgrade to a fixed version: openhab-webui 2.5.12. Check the vendor advisory for mitigations.

References

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

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