CVE-2026-81036 (GCVE-0-2026-81036)

Vulnerability from cvelistv5 – Published: 2026-08-26 15:45 – Updated: 2026-08-29 02:45
VLAI
Title
Stalwart Mail Server through 0.16.19 Authorization Code Disclosure via Unvalidated OAuth redirect_uri
Summary
Stalwart Mail Server does not compare an OAuth redirect target against any registered destination in its default configuration. The validation routine in crates/http/src/auth/oauth/registration.rs returns success immediately when the client-authentication requirement is disabled, and that requirement is false in the shipped settings, so the supplied redirect value is neither matched against a registered client nor otherwise constrained. The value is stored with the authorization code, and the login page reads it back and sends the browser to it with the code attached. A request naming a destination the attacker controls therefore delivers a valid authorization code there once the account holder authenticates, and because the token endpoint checks only that the redirect presented at exchange matches the one recorded with the code, the same party can exchange it for access and refresh tokens and read the account's mail.
Severity
8.5 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-29 02:44 UTC
CWE
  • CWE-601 - URL Redirection to Untrusted Site ('Open Redirect')
Assigner
VulnCheck CNA under the mitre root
CNA scorecard B 84/100 over 6106 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
stalwartlabs stalwart Affected: 0 , ≤ 0.16.19 (semver)
guessed Create a notification for this product.
Date Public
2026-08-26 00:00
Credits
George Chen
Show details on NVD website
To clipboard 

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