cve.bz

CVE-2026-42882

9.4 criticalEPSS 0.6%

oxyno-zeta/s3-proxy is an aws s3 proxy written in go. Prior to 5.0.0, s3-proxy contains an authentication bypass caused by inconsistent URL path interpretation between the authentication middleware and the bucket handler. The authentication middleware evaluates resource path patterns against the percent-encoded request URI (r.URL.RequestURI()), while the bucket handler constructs S3 object keys from the decoded path (r.URL.Path). This mismatch, combined with the glob library being invoked without a path separator (causing * to match across / boundaries), allows unauthenticated attackers to write to, read from, or delete objects in protected S3 namespaces. Exploitation is possible via three techniques: (1) using * patterns that match across path separators to reach protected routes via path traversal (e.g., /open/foo/drafts/../restricted/), (2) using percent-encoded slashes (%2F) to collapse multiple path segments into a single token at the auth layer while the decoded form resolves to a protected namespace at the storage layer, and (3) using dot-dot segments (../) under ** prefix patterns, where the raw path matches an open route while Go's URL parser resolves the traversal to a protected path before the bucket handler runs. An unauthenticated attacker with network access can perform unauthorized PUT, GET, or DELETE operations on objects in authentication-protected S3 namespaces. This vulnerability is fixed in 5.0.0.

CVSS 3.1
9.4CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
EPSS
0.6% chance of exploitation in the next 30 days; higher than 46% of CVEs (scores of 2026-10-26)
CWEs
CWE-22, CWE-863
Published
Modified
Record from
the NVD, synced

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
GHSA-rfgq-wgg8-662pGogithub.com/oxyno-zeta/s3-proxy<0.0.0-20260424211602-1320e4abd46a0.0.0-20260424211602-1320e4abd46a
GO-2026-5616Gogithub.com/oxyno-zeta/s3-proxy<0.0.0-20260424211602-1320e4abd46a0.0.0-20260424211602-1320e4abd46a

References

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