GHSA-rfgq-wgg8-662p · Severity: critical · Ecosystem: go — S3-Proxy has Security Issues in its Resource Path Matching Implementation
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.
Conclusion & alert: CVE-2026-42882 is rated Moderate Risk (52.2/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.20%). Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-05-22 | 0.12% | 0.20% | +0.07% |
| 2 | 2026-05-12 | — | 0.12% | — |
Full EPSS history (2 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 9.4 | 3.1 | CRITICAL |
|
3.9 | 5.5 | [email protected] |
GHSA-rfgq-wgg8-662p · Severity: critical · Ecosystem: go — S3-Proxy has Security Issues in its Resource Path Matching Implementation
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| No affected products in dataset. | |||