Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-33qg-7wpp-89cq
No affected components available
Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie. This allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid session data without knowledge of any configured secret.
Because this mechanism is used to load session state, an attacker can manipulate session contents and potentially gain unauthorized access.
Details
When secrets: is configured, Rack::Session::Cookie attempts to decrypt incoming session cookies using one of the configured encryptors. If all decrypt attempts fail, the implementation does not reject the cookie. Instead, it falls back to decoding the cookie using a default coder.
This fallback path processes attacker-controlled cookie data as trusted session state. The behavior is implicit and occurs even when encrypted cookies are expected.
The fallback decoder is applied automatically and does not require the application to opt into a non-encrypted session format. As a result, a client can send a specially crafted cookie value that bypasses the intended integrity protections provided by secrets:.
This issue affects both default configurations and those using alternative serializers for encrypted payloads.
Impact
Any Rack application using Rack::Session::Cookie with secrets: may be affected.
[!NOTE] Rails applications are typically not affected — Rails uses
ActionDispatch::Session::CookieStore, which is a separate implementation backed byActiveSupport::MessageEncryptorand does not share the vulnerable code path.
An unauthenticated attacker can supply a crafted session cookie that is accepted as valid session data. This can lead to authentication bypass or privilege escalation in applications that rely on session values for identity or authorization decisions.
Depending on application behavior and available runtime components, processing of untrusted session data may also expose additional risks.
Mitigation
- Update to a patched version of
rack-sessionthat rejects cookies when decryption fails under thesecrets:configuration.- After updating, rotate session secrets to invalidate existing session cookies, since attacker-supplied session data may have been accepted and re-issued prior to the fix.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
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.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard