ZITADEL's truncated opaque tokens are still valid

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-27840: 0.16% estimated exploitation activity in the next 30 days; percentile 5.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Opaque OIDC access tokens in 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 <tokenid:<userid. v2 tokens distinguished further where the tokenid is of the format v2<oidcsessionid-at<accesstokenid. This is an example of such a cleartext: V2354201447279099906-at354201447279165442:354201364702363650 Impact V1 token authZ/N session data is retrieved from the database using the (simple) tokenid value and userid value. The userid (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 oidcsessionid and…

Published by the source

27 Feb 2026, 21:22 UTC

Last modified by the source

27 Feb 2026, 21:22 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6mq3-xmgp-pjm5

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# Patch Next advisory brief: CVE-2026-27840

Advisory: ZITADEL's truncated opaque tokens are still valid
IDs: CVE-2026-27840, GHSA-6mq3-xmgp-pjm5
Record: https://patchnext.com/advisories/cve-2026-27840 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/zitadel/zitadel 4.11.0, 3.4.7, 1.80.0-v2.20.0.20260216092519-feab8e1fa371. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/zitadel/zitadel: affected >= 4.0.0, < 4.11.0; >= 3.0.0, < 3.4.7; >= 2.31.0, <= 2.71.19; < 1.80.0-v2.20.0.20260216092519-feab8e1fa371; fixed in 3.4.7, 1.80.0-v2.20.0.20260216092519-feab8e1fa371, 4.11.0

## Suggested inspection (read-only)
- Go github.com/zitadel/zitadel: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/zitadel/zitadel.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6mq3-xmgp-pjm5 (GitHub-reviewed advisory GHSA-6mq3-xmgp-pjm5 lists affected ranges: Go github.com/zitadel/zitadel >=4.0.0 =3.0.0 =2.31.0 =0 <1.80.0-v2.20.0.20260216092519-feab8e1fa371)

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