In OpenStack Swift before 2.38.2, the tempurl middleware does not reject the X-Copy-From header on PUT requests. A TempURL signature only covers the method, expiry, and path, and thus the list of disallowed headers is the only defense against a signed PUT request changing what the request does. An attacker holding a PUT TempURL for a single object can add an X-Copy-From header naming any object in the same account; the copy middleware copies that object to the destination, and the attacker then reads the victim's data back with a GET TempURL for the destination object. Copies across account boundaries are rejected. Only deployments using the shipped default proxy pipeline (tempurl and copy middleware) with account-level TempURL keys are affected.
Published: 2026-09-24
Updated: 2026-09-24
Base Score: 6.4
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:N
Severity: Medium
Base Score: 9.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Severity: Critical
Base Score: 5.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Severity: Medium
EPSS: 0.00226