CVE-2009-2185 in strongswan
Summary
by MITRE
The ASN.1 parser (pluto/asn1.c, libstrongswan/asn1/asn1.c, libstrongswan/asn1/asn1_parser.c) in (a) strongSwan 2.8 before 2.8.10, 4.2 before 4.2.16, and 4.3 before 4.3.2; and (b) openSwan 2.6 before 2.6.22 and 2.4 before 2.4.15 allows remote attackers to cause a denial of service (pluto IKE daemon crash) via an X.509 certificate with (1) crafted Relative Distinguished Names (RDNs), (2) a crafted UTCTIME string, or (3) a crafted GENERALIZEDTIME string.
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Analysis
by VulDB Data Team • 04/06/2025
The vulnerability described in CVE-2009-2185 represents a critical denial of service weakness within the ASN.1 parsing components of major IPsec implementations including strongSwan and openSwan. This flaw exists in the pluto IKE daemon which processes X.509 certificates during the Internet Key Exchange protocol negotiation phase. The vulnerability stems from insufficient validation of ASN.1 encoded data structures, specifically affecting the parsing of Relative Distinguished Names, UTCTIME, and GENERALIZEDTIME elements within X.509 certificates. The flaw manifests when the parser encounters malformed or crafted certificate data that triggers unexpected behavior in the parsing logic, leading to daemon crashes and complete service disruption for affected systems. This vulnerability operates at the intersection of cryptographic protocol implementation and software security, where improper input validation leads to system instability.
The technical implementation of this vulnerability exploits weaknesses in the ASN.1 parser's handling of time-related certificate fields and hierarchical naming structures. When processing X.509 certificates containing crafted Relative Distinguished Names, the parser fails to properly validate the structure and content of these elements, causing memory corruption or control flow exceptions that result in daemon termination. Similarly, when encountering malformed UTCTIME or GENERALIZEDTIME strings, the parser's time parsing functions lack adequate bounds checking and format validation, leading to stack overflows or other memory-related issues that crash the pluto daemon. This represents a classic buffer overflow scenario where insufficient input sanitization allows attackers to manipulate the parser's execution path through carefully constructed certificate data. The vulnerability is categorized under CWE-121 as heap-based buffer overflow and CWE-125 as out-of-bounds read, both of which are well-documented patterns in ASN.1 parser implementations.
The operational impact of CVE-2009-2185 extends beyond simple service disruption to encompass broader network security implications for organizations relying on IPsec VPN infrastructure. When exploited, the vulnerability can cause cascading failures in secure communication channels, potentially affecting thousands of connected devices and users who depend on these VPN services for remote access. The attack requires minimal privileges as it operates over the network protocol layer, making it particularly dangerous for public-facing VPN gateways. The vulnerability affects multiple versions across different software lines, indicating a widespread issue in the IPsec ecosystem and suggesting that attackers can target various implementations without requiring specific version identification. This makes the vulnerability particularly attractive to threat actors seeking to disrupt services or perform reconnaissance on network infrastructure. The impact is consistent with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage protocol implementation flaws to cause service unavailability.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to address the ASN.1 parsing deficiencies in both strongSwan and openSwan implementations. Organizations should prioritize updating to patched versions where available, specifically strongSwan 2.8.10, 4.2.16, and 4.3.2, along with openSwan 2.6.22 and 2.4.15. Network administrators should implement certificate validation policies that include strict ASN.1 format checking and reject certificates containing malformed time fields or unusual RDN structures. Additionally, implementing monitoring solutions that detect daemon crashes or restart patterns can help identify exploitation attempts. The vulnerability highlights the importance of robust input validation in cryptographic libraries and demonstrates the need for comprehensive testing of ASN.1 parsing components against malformed inputs. Organizations should also consider implementing certificate pre-validation mechanisms that test certificate structures before accepting them into the IPsec processing pipeline, thereby preventing exploitation of this class of vulnerabilities.