CVE-2008-5161 in Tectia Client
Summary
by MITRE
Error handling in the SSH protocol in (1) SSH Tectia Client and Server and Connector 4.0 through 4.4.11, 5.0 through 5.2.4, and 5.3 through 5.3.8; Client and Server and ConnectSecure 6.0 through 6.0.4; Server for Linux on IBM System z 6.0.4; Server for IBM z/OS 5.5.1 and earlier, 6.0.0, and 6.0.1; and Client 4.0-J through 4.3.3-J and 4.0-K through 4.3.10-K; and (2) OpenSSH 4.7p1 and possibly other versions, when using a block cipher algorithm in Cipher Block Chaining (CBC) mode, makes it easier for remote attackers to recover certain plaintext data from an arbitrary block of ciphertext in an SSH session via unknown vectors.
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability described in CVE-2008-5161 represents a critical flaw in secure shell implementations that affects multiple SSH Tectia and OpenSSH versions. This weakness specifically targets the error handling mechanisms within SSH protocol implementations when utilizing block cipher algorithms in Cipher Block Chaining mode, creating a pathway for attackers to potentially recover plaintext data from intercepted ciphertext. The vulnerability spans across numerous versions of SSH Tectia products including Client and Server components across multiple release lines, as well as various OpenSSH versions including the 4.7p1 release, making it particularly widespread in affected deployments. The flaw operates through a sophisticated exploitation vector that leverages the inherent properties of CBC mode encryption combined with specific error handling patterns in these implementations.
The technical nature of this vulnerability stems from improper error handling during SSH protocol operations when block ciphers are employed in CBC mode. In standard cryptographic operations, CBC mode requires that each ciphertext block be processed through an initialization vector and previous ciphertext blocks to maintain data integrity and confidentiality. However, when error conditions occur during these operations, the affected SSH implementations fail to properly handle these scenarios, creating information leakage channels. Attackers can exploit this by carefully crafting specific inputs or observing error responses that reveal information about the underlying plaintext data. This type of vulnerability falls under the CWE-20 category of "Improper Input Validation" and specifically relates to cryptographic weaknesses in error handling mechanisms. The vulnerability allows for a form of chosen ciphertext attack where an attacker can manipulate the cryptographic operations to extract information about the plaintext without possessing the encryption keys.
The operational impact of CVE-2008-5161 is significant for organizations relying on affected SSH implementations, as it creates a potential pathway for data compromise during SSH sessions. Attackers can potentially recover sensitive information from intercepted SSH communications, including authentication credentials, configuration data, and other confidential information transmitted through the encrypted channels. The vulnerability is particularly concerning because it affects both client and server implementations, meaning that either endpoint in an SSH session could be exploited. Additionally, the fact that this vulnerability affects OpenSSH 4.7p1 and potentially other versions indicates that organizations may be exposed across multiple platforms and implementations. The attack vectors are not fully specified in the CVE description, but typically such vulnerabilities allow for passive observation of network traffic and subsequent analysis of error responses to reconstruct plaintext data. This weakness directly impacts the confidentiality guarantees provided by SSH protocol implementations and can lead to unauthorized access to systems and data.
Organizations affected by this vulnerability should implement immediate mitigations to protect their SSH infrastructure. The primary recommendation involves upgrading to patched versions of the affected SSH implementations, as vendors have released updates addressing the specific error handling issues. For environments where immediate upgrades are not feasible, administrators can implement workarounds such as disabling CBC mode cipher suites and using alternative encryption modes that are less susceptible to this type of attack. The ATT&CK framework categorizes this vulnerability under the "Cryptographic Operations" and "Data Exposure" tactics, as it enables adversaries to gain access to encrypted data through exploitation of cryptographic implementation weaknesses. Security teams should also implement enhanced monitoring of SSH traffic for unusual error patterns and consider implementing network segmentation to limit the potential impact of successful exploitation attempts. Regular security assessments and vulnerability scanning should be performed to identify any remaining instances of affected software versions within the organization's infrastructure.