CVE-2026-88018 is a critical-severity (CVSS 9.8) Improper Authentication vulnerability. O3 Security confirms whether CVE-2026-88018 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.75.1, rclone serve s3 configured with --auth-proxy but without…
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-88018.
Description
rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.75.1, rclone serve s3 configured with --auth-proxy but without --auth-key allows authPairMiddleware to register any client-chosen accessKeyID with an empty ws.s3Secret. gofakes3 then verifies the request’s SigV4 signature against that same empty secret, while Server.auth passes the access key identifier as both the user and authentication value to the proxy without an independent per-identity secret. An unauthenticated network attacker can therefore choose an arbitrary access key, sign with an empty secret, and reach whatever backend the auth-proxy script resolves for that identity. This issue is fixed in version 1.75.1.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-88018 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-88018 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-88018. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-88018 in your dependencies?
O3 detects CVE-2026-88018 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.