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Fencer Intel
medium 5.5

CVE-2025-27136 json

LocalS3 CreateBucketConfiguration Endpoint XML External Entity (XXE) Injection

published last yr. modified 4mo ago also GHSA-g6wm-2v64-wq36 , EUVD-2025-7729

cvss
5.5
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

LocalS3 is an Amazon S3 mock service for testing and local development. Prior to version 1.21, the LocalS3 service's bucket creation endpoint is vulnerable to XML External Entity (XXE) injection. When processing the CreateBucketConfiguration XML document during bucket creation, the service's XML parser is configured to resolve external entities. This allows an attacker to declare an external entity that references an internal URL, which the server will then attempt to fetch when parsing the XML. The vulnerability specifically occurs in the location constraint processing, where the XML parser resolves external entities without proper validation or restrictions. When the external entity is resolved, the server makes an HTTP request to the specified URL and includes the response content in the parsed XML document. This vulnerability can be exploited to perform server-side request forgery (SSRF) attacks, allowing an attacker to make requests to internal services or resources that should not be accessible from external networks. The server will include the responses from these internal requests in the resulting bucket configuration, effectively leaking sensitive information. The attacker only needs to be able to send HTTP requests to the LocalS3 service to exploit this vulnerability.

Patch / fix

  • maven io.github.robothy:local-s3-rest 1.21

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P
CNA 4.0 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
maven io.github.robothy:local-s3-rest
<1.21
1.21

Affected products

  • Robothy local-s3

Classification

Weakness
  • CWE-611 Improper Restriction of XML External Entity Reference

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.