{"schemaVersion":3,"id":"CVE-2021-29492","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"Envoy is a cloud-native edge/middle/service proxy. Envoy does not decode escaped slash sequences `%2F` and `%5C` in HTTP URL paths in versions 1.18.2 and before. A remote attacker may craft a path with escaped slashes, e.g. `/something%2F..%2Fadmin`, to bypass access control, e.g. a block on `/admin`. A backend server could then decode slash sequences and normalize path and provide an attacker access beyond the scope provided for by the access control policy. ### Impact Escalation of Privileges when using RBAC or JWT filters with enforcement based on URL path. Users with back end servers that interpret `%2F` and `/` and `%5C` and `\\` interchangeably are impacted. ### Attack Vector URL paths containing escaped slash characters delivered by untrusted client. Patches in versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. As a workaround, if back end servers treat `%2F` and `/` and `%5C` and `\\` interchangeably and a URL path based access control is configured, one may reconfigure the back end server to not treat `%2F` and `/` and `%5C` and `\\` interchangeably.","dates":{"published":"2021-05-28T21:00:24.000Z","modified":"2024-08-03T22:11:05.253Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":8.3,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":8.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":8.3,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L","exploitability":null,"impact":null,"computed":false},{"version":"2.0","versionLabel":"v2.0","source":"NVD","score":7.5,"severity":"high","vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.66214,"percentile":0.99274,"severity":"critical","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.66214},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.66214,"percentile":0.99274}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.66214,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.66214,"percentile":null}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