Dyad EUVD-2026-103669

Requires that Dyad (≤1.16.0) is installed on the victim's machine with its dyad:// custom-protocol handler registered, and that the victim is induced to trigger a crafted OAuth callback deep link (UI:P passive user interaction). The specific defect: the OAuth Callback Handler processed unsolicited or unmatched custom-protocol callbacks (delivered via open-url, argv, or second-instance) and performed the credential write without requiring a provider-bound, expiring, single-use correlation value minted at flow start - so a callback that did not originate from a legitimate in-app connection flow was still honored. Limiting factors that reduce realistic risk: mandatory user interaction to launch the protocol link, the need for the desktop app to be installed and running, and an integrity-only, LOW-rated impact (no confidentiality or availability loss per CVSS).

This is a low-to-moderate real-world priority despite the medium CVSS 4.0 base score of 5.3. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N) shows a remotely-reachable, unauthenticated, low-complexity flaw but with only LOW integrity impact and NO confidentiality or availability impact, and crucially it requires passive user interaction (UI:P) - the victim must be induced to trigger a malicious custom-protocol (dyad://) callback. No EPSS score, CISA KEV listing, or public POC is present in the supplied data, so there is no signal of active exploitation or automatable mass exploitation; the SSVC exploitation maturity is effectively 'none' (E:X = Not Defined). The threat is best characterized as opportunistic/targeted social-engineering rather than widespread. Note that the CWE (CWE-352, CSRF) and the patch evidence are mutually consistent: the fix introduces a provider-bound, expiring, single-use correlation value for OAuth callbacks, confirming the CSRF framing. The main uncertainty is the concrete impact of a forged OAuth credential write - the CVSS caps it at VI:L, but a successful attacker-controlled token write to a victim's integration could have higher practical consequence than the score suggests; verify downstream blast radius against the vendor advisory GHSA-pqj5-w36j-2839.

An attacker crafts a malicious dyad:// deep link embedding an OAuth callback carrying attacker-controlled credentials and lures a victim who has Dyad installed into clicking it (e.g., via a web page or message). Because the OAuth Callback Handler accepted unsolicited/unmatched callbacks without validating a flow-bound correlation value, the application performs a credential write tied to the attacker's tokens rather than rejecting the unsolicited return. No public exploit code was identified at time of analysis, and the attack depends on user interaction (UI:P) to deliver the forged callback.