rclone EUVD-2026-109451

Requires a running rclone serve webdav instance that relies on authentication via --user/--pass, --htpasswd or --auth-proxy, reachable by the attacker over the network; no credentials, user interaction or non-default settings are otherwise needed, since the auth middleware exempts every OPTIONS request. Exploitation is strictly limited to the OPTIONS method and to affected versions 1.64.0 through 1.75.1. Key limiting factors: only serve webdav is vulnerable (the advisory confirms serve http, serve restic and rcd are not, as they do not route OPTIONS to a path-stating handler), and the disclosure is metadata-only - existence and file-vs-collection type of a named path - with no file contents, directory listings or write access obtainable this way.

This is a genuine but bounded issue, best characterized as a moderate-priority information-disclosure flaw rather than a critical break. The supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) confirms a network-reachable, low-complexity, unauthenticated vector with no user interaction, which is why it scores 6.9; crucially, impact is limited to low confidentiality (VC:L) with no integrity or availability effect (VI:N/VA:N), matching the advisory's statement that only metadata - existence and type of a path - leaks, never file contents, listings or writes. The vuln.today decision label is 'this_month' (not act_now/emergency), consistent with a real-but-not-urgent prioritization. No EPSS score and no KEV listing were provided, and the flaw is NOT in CISA KEV, so there is no evidence of active exploitation; however, a detailed, reporter-verified proof-of-concept is published in the GHSA advisory, so exploitability is proven even if in-the-wild use is not. The signals are internally consistent rather than conflicting: easy to trigger, but the ceiling on damage (an existence/type oracle for enumeration) keeps real-world risk moderate and contingent on exposing serve webdav to untrusted networks.

An attacker who can reach an internet- or network-exposed rclone serve webdav endpoint that is protected by --user/--pass, --htpasswd or --auth-proxy sends unauthenticated OPTIONS requests against candidate paths and reads the Allow response header, which differs for an existing file, an existing collection and a missing path. By iterating candidate names one request each, they enumerate the served namespace - often sensitive directory and file names - as reconnaissance before a further attack. A reproducible PoC verified by the reporter is published in the vendor's GHSA advisory.