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GHSA-8m7c-hf24-5g47
No affected components available
Summary
Two concurrent token-exchange requests using the same OAuth authorization code could
each mint a distinct valid (access_token, refresh_token) pair, breaking the
single-use guarantee that PKCE relies on.
Details
The token-exchange flow read is_used and called markAsUsed as an unconditional
update at the end of the path. A new OAuthAuthorizationCode.claimByCode method now
performs an atomic compare-and-swap (WHERE code = ? AND is_used = false) and is
called immediately before OAuthToken.insert, after redirect-URI, PKCE, and client
authentication have all succeeded. Only the first concurrent caller's UPDATE wins;
the rest see invalid_grant: Authorization code has already been used.
Impact
An attacker who has observed an authorization code and the corresponding PKCE verifier (for example through a malicious OAuth-aware client or by racing a real exchange) could obtain a long-lived refresh token in addition to the legitimate one.
Credit
This issue was reported by @eddieran.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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