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CVE-2026-81036— Stalwart Mail Server through 0.16.19 Authorization Code Disclosure via Unvalidated OAuth redirect_uri

Quick assessment

Affected
stalwartlabs stalwart
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Stalwart Mail Server 在默认配置下不会将 OAuth 重定向目标与任何已注册的目的地进行比对。 在 中的验证例程，当“客户端认证”要求被禁用时会立即返回成功。而在随软件发行的默认设置中，该要求被设为 ，因此提供的重定向值既未与任何已注册的客户端进行匹配，也未受到其他约束。 该值会与授权码一起存储。在登录页面读取该值后，浏览器会被重定向到该地址，并附带授权码。如果攻击者指定一个由其控制的目的地，那么当账户持有人完成认证后，有效的授权码就会被发送到攻击者控制的地址。此外，由于令牌端点在交换授权码时仅

CVSS 8.1 · High

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
stalwartlabs stalwart ≤ 0.16.19 affected
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I. Basic Information for CVE-2026-81036

Vulnerability Information
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Vulnerability Title
Stalwart Mail Server through 0.16.19 Authorization Code Disclosure via Unvalidated OAuth redirect_uri
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
指向未可信站点的URL重定向(开放重定向)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
stalwartlabs stalwart 0 ~ 0.16.19 -

II. Public POCs for CVE-2026-81036

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 8344 chars
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III. Intelligence Information for CVE-2026-81036

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Patches & Fixes for CVE-2026-81036 (2)

Vendor Advisories for CVE-2026-81036 (1)

Vendor Pages for CVE-2026-81036 (1)

IV. Related Vulnerabilities

Same product: stalwart
Same vendor: stalwartlabs
Same weakness: CWE-601

V. Comments for CVE-2026-81036

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