{"cve":"CVE-2026-27840","nvd":{"published":"2026-02-26T01:16:25.103","modified":"2026-06-17T10:27:46.473","status":"Analyzed","description":"ZITADEL is an open source identity management platform. Starting in version 2.31.0 and prior to versions 3.4.7 and 4.11.0, opaque OIDC access tokens in the v2 format truncated to 80 characters are still considered valid.  Zitadel uses a symmetric AES encryption for opaque tokens. The cleartext payload is a concatenation of a couple of identifiers, such as a token ID and user ID. Internally Zitadel has 2 different versions of token payloads. v1 tokens are no longer created, but are still verified as to not invalidate existing session after upgrade. The cleartext payload has a format of `<token_id>:<user_id>`. v2 tokens distinguished further where the `token_id` is of the format `v2_<oidc_session_id>-at_<access_token_id>`. V1 token authZ/N session data is retrieved from the database using the (simple) `token_id` value and `user_id` value. The `user_id` (called `subject` in some parts of our code) was used as being the trusted user ID. V2 token authZ/N session data is retrieved from the database using the `oidc_session_id` and `access_token_id` and in this case the `user_id` from the token is ignored and taken from the session data in the database. By truncating the token to 80 chars, the user_id is now missing from the cleartext of the v2 token. The back-end still accepts this for above reasons. This issue is not considered exploitable, but may look awkward when reproduced. The patch in versions 4.11.0 and 3.4.7 resolves the issue by verifying the `user_id` from the token against the session data from the database. No known workarounds are available.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N","score":4.3},"cwes":["CWE-302"],"references":["https://github.com/zitadel/zitadel/releases/tag/v3.4.7","https://github.com/zitadel/zitadel/releases/tag/v4.11.0","https://github.com/zitadel/zitadel/security/advisories/GHSA-6mq3-xmgp-pjm5"],"products":["zitadel:zitadel"],"source":"nvd","synced_at":"2026-10-19T22:24:17.937441719+00:00"},"epss":{"cve":"CVE-2026-27840","score":0.00159,"percentile":0.05021,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-6mq3-xmgp-pjm5","url":"https://osv.dev/vulnerability/GHSA-6mq3-xmgp-pjm5","summary":"ZITADEL's truncated opaque tokens are still valid","modified":"2026-03-23T04:56:27.999492675Z","packages":[{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":[">=4.0.0 <4.11.0"],"fixed":["4.11.0"]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":[">=3.0.0 <3.4.7"],"fixed":["3.4.7"]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":[">=2.31.0 <=2.71.19"],"fixed":[]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":["<1.80.0-v2.20.0.20260216092519-feab8e1fa371"],"fixed":["1.80.0-v2.20.0.20260216092519-feab8e1fa371"]}]},{"id":"GO-2026-4573","url":"https://osv.dev/vulnerability/GO-2026-4573","summary":"ZITADEL's truncated opaque tokens are still valid in github.com/zitadel/zitadel","modified":"2026-03-23T04:52:45.687870Z","packages":[{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/zitadel/zitadel","purl":"pkg:golang/github.com/zitadel/zitadel","ranges":["<1.80.0-v2.20.0.20260216092519-feab8e1fa371"],"fixed":["1.80.0-v2.20.0.20260216092519-feab8e1fa371"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}