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CVE-2021-21266

18
FAUCET Score

CVE-2021-21266 is an XML External Entity (XXE) vulnerability affecting openHAB versions prior to 2.5.12 and 3.0.1, impacting numerous add-ons that parse external XML. Attackers on the same network can exploit this to retrieve internal file system information, with SSDP requests being a potential vector. The vulnerability has a CVSS score of 5.0 (Medium), indicating a network-based attack with low complexity and no user interaction, leading to low confidentiality impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.5.12CPE matchmatch criteria
cpe:2.3:a:openhab:openhab:*:*:*:*:*:*:*:*
3.0.0CPE matchmatch criteria
cpe:2.3:a:openhab:openhab:3.0.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.4MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.1
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.10%
Probability of exploitation in next 30 days
EPSS Percentile
62.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0110 is in the 76th percentile among its peer group of 21,974 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

dev.to / brianverm/configure-your-java-xml-parsers-to-prevent-xxe-213c
Third Party Advisory
github.com / openhab/openhab-addons/commit/81935b0ab126e6d9aebd2f6c3fc67d82bb7e8b86
PatchThird Party Advisory
github.com / openhab/openhab-addons/security/advisories/GHSA-r2hc-pmr7-4c9r
PatchThird Party Advisory
contrastsecurity.com / security-influencers/xml-xxe-pitfalls-with-jaxb
Technical DescriptionThird Party Advisory