CVE-2017-9022 in strongSwan
Summary
by MITRE
The gmp plugin in strongSwan before 5.5.3 does not properly validate RSA public keys before calling mpz_powm_sec, which allows remote peers to cause a denial of service (floating point exception and process crash) via a crafted certificate.
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Analysis
by VulDB Data Team • 12/04/2025
The vulnerability identified as CVE-2017-9022 affects the gmp plugin within strongSwan versions prior to 5.5.3, representing a critical security flaw that undermines the integrity of the IPsec VPN implementation. This issue stems from insufficient validation of RSA public keys during the certificate processing phase, creating a pathway for remote attackers to exploit the system through carefully crafted certificates. The vulnerability specifically targets the mpz_powm_sec function call within the GNU Multiple Precision Arithmetic Library, which is utilized for modular exponentiation operations in RSA cryptography. The flaw manifests when the system fails to properly verify the structure and validity of RSA public keys before executing cryptographic operations, leading to unpredictable behavior in the underlying mathematical computations.
The technical execution of this vulnerability occurs during the certificate validation process when strongSwan receives a malformed RSA public key from a remote peer. The gmp plugin does not perform adequate checks to ensure that the RSA public key components meet the required mathematical specifications before invoking mpz_powm_sec. This function expects valid input parameters to perform modular exponentiation securely, but when provided with malformed or specially crafted RSA key data, it can trigger floating point exceptions or other arithmetic errors. The improper validation allows attackers to construct certificates containing invalid RSA public key parameters that cause the cryptographic library to behave unpredictably, ultimately resulting in process crashes and system instability. This represents a classic example of a malformed input handling vulnerability that can be exploited for denial of service attacks.
The operational impact of CVE-2017-9022 extends beyond simple service disruption, as it can severely compromise the availability and reliability of IPsec VPN services that rely on strongSwan implementations. Organizations using vulnerable versions of strongSwan face the risk of unauthorized denial of service attacks that can render their VPN infrastructure unavailable to legitimate users, potentially disrupting business operations and communications. The vulnerability is particularly concerning because it can be exploited remotely without requiring authentication or prior access to the system, making it an attractive target for attackers seeking to disrupt network services. The floating point exceptions and process crashes can lead to complete service outages, forcing administrators to restart services and potentially causing temporary loss of network connectivity for users relying on the affected VPN infrastructure.
This vulnerability aligns with CWE-248, which addresses "Exception Handling Errors" in software systems, and demonstrates the importance of proper input validation in cryptographic implementations. The flaw also relates to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion or system instability. Organizations should implement immediate mitigations including upgrading to strongSwan version 5.5.3 or later, which contains the necessary patches to properly validate RSA public keys before cryptographic operations. Additional protective measures include implementing certificate validation policies that reject certificates with suspicious key parameters and monitoring for unusual process crashes or system instability that may indicate exploitation attempts. Security teams should also consider network-level protections such as rate limiting and intrusion detection systems to help identify and prevent exploitation attempts targeting this vulnerability.