{"id":"CVE-2026-72887","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-72887","generatedAt":"2026-10-28T00:25:51.655Z","title":"Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token.","description":"Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token.\n\nPassing a callback to the constructor selects OAuth 1.0a. get_request_token then revokes that choice when the request token response omits oauth_callback_confirmed, with no exception, no warning and no option to require 1.0a. The access token request is built from the OAuth 1.0 message class, which has no verifier parameter, so oauth_verifier is dropped from the request even when get_access_token was passed one.\n\noauth_verifier is the binding that OAuth 1.0a added between the authorization step and the token exchange. An application that asked for 1.0a and gets 1.0 is open to OAuth 1.0 session fixation, where an attacker obtains a request token, has the victim authorize it, and then completes the exchange themselves, linking the victim's provider account to a session the attacker controls. No attacker action sets up the downgrade: a provider that does not confirm the callback is enough.","published":"2026-08-16T14:16:55.000Z","lastModified":"2026-08-26T16:51:19.000Z","status":"Deferred","sourceIdentifier":"9b29abf9-4ab0-4765-b253-1875cd9b441e","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-757"],"affected":[],"epss":{"score":0.00721,"percentile":0.53679,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.72%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://datatracker.ietf.org/doc/html/rfc5849#section-2.1","source":"9b29abf9-4ab0-4765-b253-1875cd9b441e"},{"url":"https://datatracker.ietf.org/doc/html/rfc5849#section-2.3","source":"9b29abf9-4ab0-4765-b253-1875cd9b441e"},{"url":"https://github.com/vurtdev/Net-OAuth/commit/fd505dac1988723ed96721657663f2e4ac731644.patch","source":"9b29abf9-4ab0-4765-b253-1875cd9b441e"},{"url":"https://github.com/vurtdev/Net-OAuth/security/advisories/GHSA-jh72-4qq2-8j6g","source":"9b29abf9-4ab0-4765-b253-1875cd9b441e"},{"url":"https://metacpan.org/release/RRWO/Net-OAuth-0.32/changes","source":"9b29abf9-4ab0-4765-b253-1875cd9b441e"},{"url":"http://www.openwall.com/lists/oss-security/2026/08/16/3","source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-72887","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}