CVE-2026-89312 in Google
Summary
by MITRE • 10/23/2026
`AesGcmCryptor.Open` passed a caller-supplied nonce straight to `cipher.AEAD.Open` without checking its length. The Go standard library **panics** rather than returning an error when a GCM nonce is not exactly `NonceSize()` bytes, so a JWE carrying a wrong-sized IV crashes the decrypting goroutine.
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Analysis
by VulDB Data Team • 10/23/2026
The vulnerability identified in the AesGcmCryptor.Open function represents a critical input validation failure within the cryptographic implementation of JSON Web Encryption (JWE) processing. The core technical flaw lies in the direct pass-through of caller-supplied nonce data to the underlying Go standard library's cipher.AEAD.Open method without performing any preliminary length verification. In secure software design, it is imperative that all external inputs, particularly those influencing cryptographic operations such as initialization vectors or nonces, undergo strict validation against expected parameters before being utilized by sensitive subsystems. By omitting this check, the application fails to enforce a fundamental security boundary, allowing malformed data structures to propagate directly into the encryption engine where they trigger an unrecoverable runtime exception rather than a controlled error response.
This specific implementation detail exploits the behavior of the Go programming language's standard library regarding Galois/Counter Mode (GCM) operations. When AES-GCM is used for authenticated encryption, it requires a nonce that matches exactly the size defined by NonceSize(), which is typically twelve bytes for this algorithm variant. If the provided nonce deviates from this exact length, the Go runtime does not return an error code or exception object that can be caught and handled gracefully; instead, it triggers a panic. A panic in Go causes the current goroutine to terminate abruptly and unwind its stack, effectively crashing the specific thread of execution responsible for decrypting the JWE payload. This behavior transforms what should have been a simple data validation failure into a severe availability issue, as the crash can propagate depending on how the application handles panics across different parts of the system architecture.
The operational impact of this vulnerability is primarily centered around Denial of Service (DoS). An attacker who can supply JWE tokens with incorrectly sized initialization vectors or nonces can systematically trigger these crashes in decrypting goroutines. In a web service context, where each request might spawn new goroutines to handle decryption tasks, repeated exploitation could lead to resource exhaustion if the application attempts to restart crashed goroutines without proper limits, or it may simply result in unhandled panics that crash the entire server process depending on global panic recovery mechanisms. This allows an adversary with network access to disrupt service availability for legitimate users by sending a small number of crafted requests containing malformed cryptographic parameters. The impact is particularly severe because it requires no authentication bypass or complex exploitation chain; merely submitting a JWE with a nonce length that does not match the expected constant is sufficient to cause disruption.
From a standards perspective, this vulnerability aligns closely with CWE-20 Improper Input Validation and CWE-754: Improper Check for Unusual or Exceptional Conditions. The failure to validate input size before use violates best practices outlined in secure coding guidelines which mandate that all external data be validated against expected formats and lengths prior to processing. Furthermore, this behavior can be mapped to the MITRE ATT&CK framework under T1499: Endpoint Denial of Service or T1529: System Shutdown/Reboot if the panic leads to a full process crash. The lack of graceful error handling means that the system fails to degrade gracefully when encountering invalid inputs, instead opting for catastrophic failure modes that are easily exploitable by remote attackers.
To mitigate this vulnerability, developers must implement explicit length checks on all cryptographic parameters before passing them to lower-level cipher functions. Specifically, the AesGcmCryptor.Open function should verify that the provided nonce has a length equal to aesgcm.NonceSize() and return a descriptive error if it does not. This ensures that invalid inputs are handled as logical errors rather than runtime crashes. Additionally, implementing global panic recovery mechanisms at the HTTP handler or service layer can provide an additional safety net, ensuring that unexpected panics do not bring down the entire application instance. However, relying solely on panic recovery is insufficient; input validation must be the primary defense to maintain system stability and security integrity. Regular code audits focusing on cryptographic API usage patterns are recommended to identify similar oversights in other parts of the codebase where standard library functions with strict parameter requirements are invoked without adequate pre-checks.