CVE-2015-2774 in Erlang
Summary
by MITRE
Erlang/OTP before 18.0-rc1 does not properly check CBC padding bytes when terminating connections, which makes it easier for man-in-the-middle attackers to obtain cleartext data via a padding-oracle attack, a variant of CVE-2014-3566 (aka POODLE).
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Analysis
by VulDB Data Team • 07/12/2022
The vulnerability identified as CVE-2015-2774 affects Erlang/OTP versions prior to 18.0-rc1 and represents a critical cryptographic flaw that undermines the security of encrypted communications. This issue stems from improper validation of CBC (Cipher Block Chaining) padding bytes during connection termination processes, creating a significant weakness that adversaries can exploit to compromise encrypted data transmission. The vulnerability operates within the cryptographic protocol stack of Erlang/OTP, which is widely used in distributed systems and telecommunications infrastructure, making it particularly concerning for organizations relying on these platforms for secure communications.
The technical flaw manifests when the system fails to properly verify the integrity of CBC padding bytes during the TLS connection termination phase. This improper validation creates a padding-oracle condition that allows attackers to systematically determine the plaintext content of encrypted messages through carefully crafted attacks. The vulnerability is specifically related to how the system handles padding validation during the decryption process, where the error responses provided during padding failures can be used to infer information about the underlying plaintext. This behavior directly aligns with the principles of padding-oracle attacks as seen in the POODLE vulnerability (CVE-2014-3566), where attackers exploit the timing differences in error responses to gradually reconstruct encrypted data. The flaw essentially provides an oracle that reveals whether padding bytes are correctly formatted, enabling attackers to perform iterative decryption attempts.
The operational impact of this vulnerability extends beyond simple data exposure, as it fundamentally compromises the confidentiality guarantees of TLS-encrypted communications within Erlang/OTP applications. Attackers can leverage this weakness to perform man-in-the-middle attacks that allow them to recover cleartext data from encrypted sessions without requiring direct access to the encryption keys. This vulnerability particularly affects systems that use Erlang/OTP for secure communication protocols such as XMPP, SIP, and other messaging systems that rely on TLS encryption. The consequences include potential exposure of sensitive user data, session hijacking capabilities, and the ability to manipulate communication content, making it a significant threat to organizations deploying Erlang-based systems in environments where data confidentiality is paramount.
Organizations should prioritize immediate remediation by upgrading to Erlang/OTP version 18.0-rc1 or later, which implements proper padding validation mechanisms. Additional mitigations include implementing strict TLS configuration policies that disable vulnerable cipher suites, deploying network monitoring solutions to detect anomalous padding behavior, and conducting comprehensive security assessments of all Erlang/OTP-based systems. The vulnerability demonstrates the importance of proper cryptographic implementation practices and highlights the need for rigorous validation of padding mechanisms in cryptographic protocols. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through protocol manipulation and can be categorized under initial access and privilege escalation vectors. Organizations should also consider implementing additional layers of security such as network segmentation, encryption key rotation, and comprehensive logging to detect and respond to potential exploitation attempts, as the vulnerability can be leveraged in conjunction with other attack vectors to achieve more comprehensive system compromise.