EUVD-2026-65540
GHSA-mwgh-564g-j9ww
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/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
Network vector but requires a specific same-host scheme-downgrade redirect plus on-path interception (AC:H); impact is disclosure of the STS token only, so C:H with I:N/A:N.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/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
Lifecycle Timeline
4DescriptionCVE.org
rclone before 1.74.4 fails to strip the X-Amz-Security-Token header when an S3 redirect changes scheme from HTTPS to HTTP on the same host. Attackers can intercept plaintext HTTP traffic to capture AWS STS session tokens sent in request headers.
AnalysisAI
Cleartext disclosure of AWS STS session tokens affects rclone before 1.74.4 when its S3 backend follows a redirect that keeps the same host:port but downgrades the scheme from HTTPS to HTTP. The redirect-safety logic added in v1.74.3 (commit e7b1eb774) compares only URL.Host and ignores URL.Scheme, so the X-Amz-Security-Token header is re-sent over the now-plaintext connection, letting any passive observer on the path harvest the temporary credential. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the rclone S3 backend to be configured with temporary AWS credentials that include an STS session_token (assumed-role, CI, or Kubernetes IRSA setups), AND the configured S3 endpoint (via s3 remote or --s3-endpoint) to respond with a 3xx redirect to the same host:port that downgrades the scheme from https:// to http://, AND a passive attacker positioned on the resulting plaintext network path to read request headers. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The published CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H, score 9.3) rates this Critical with high impact across confidentiality, integrity, and availability, but that appears aggressive relative to the described mechanism: the primary, directly-caused effect is disclosure of an STS session token (a confidentiality loss), while integrity/availability impact is only indirect and contingent on what the captured token can subsequently do. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An operator configures an rclone S3 remote against a self-hosted or third-party S3-compatible endpoint using assumed-role temporary credentials, so requests carry an X-Amz-Security-Token header. The endpoint (compromised, or misconfigured behind a TLS front) answers a request with a 3xx redirect to the identical host:port over http:// instead of https://; rclone treats it as 'same host,' follows it, and re-sends the STS token in cleartext, where a passive on-path observer captures it and reuses it until it expires. … |
| Remediation | Vendor-released patch: 1.74.4 - upgrade rclone to 1.74.4 or later, which extends the redirect check to compare URL.Scheme in addition to host (fix commit https://github.com/rclone/rclone/commit/1a28451ea6fc8ac1806b0e9923dcb5b3f543f7fa; advisory GHSA-gx4c-2hqx-cw2r). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all rclone instances with S3 backends and identify those operating on internet-exposed or untrusted network paths where HTTP redirects might occur. …
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