CVE-2018-15587 in Evolution
Summary
by MITRE
GNOME Evolution through 3.28.2 is prone to OpenPGP signatures being spoofed for arbitrary messages using a specially crafted email that contains a valid signature from the entity to be impersonated as an attachment.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2018-15587 affects GNOME Evolution versions up to 3.28.2 and represents a critical security flaw in OpenPGP signature verification mechanisms. This issue stems from improper handling of cryptographic signatures when multiple signatures are present in email messages, creating a scenario where attackers can manipulate the display of signature information to deceive users. The vulnerability specifically impacts the email client's ability to correctly associate digital signatures with their corresponding message content, allowing for sophisticated social engineering attacks that exploit user trust in cryptographic verification processes.
The technical root cause of this vulnerability lies in how GNOME Evolution processes OpenPGP signatures when they appear as attachments within email messages. When an email contains both a main message with a signature and an attachment that also contains a valid signature from a different entity, the client fails to properly validate the relationship between the signature and the message content. This flaw creates a situation where the system may display a valid signature from one party while the actual message content has been modified or impersonated by another entity. The vulnerability operates at the application layer and specifically affects the cryptographic verification logic within the email client's OpenPGP implementation.
The operational impact of this vulnerability extends beyond simple message integrity concerns, as it enables sophisticated phishing and impersonation attacks that can bypass traditional security measures. An attacker could craft an email that appears to contain a valid signature from a trusted contact while actually delivering malicious content, potentially leading to unauthorized access to sensitive information or systems. This vulnerability particularly affects enterprise environments where users rely on cryptographic signatures for verifying message authenticity, and it can be exploited to undermine trust in the email verification process. The attack vector requires minimal user interaction beyond opening the malicious email, making it particularly dangerous in targeted campaigns.
Organizations should implement immediate mitigations including upgrading to GNOME Evolution version 3.28.3 or later, which contains the necessary patches to address the signature verification flaw. Additionally, security teams should consider implementing additional email filtering rules that can detect and quarantine suspicious email patterns involving multiple signatures or unusual attachment structures. Network administrators should also monitor for potential exploitation attempts through email traffic analysis, looking for indicators of signature manipulation attempts. The vulnerability aligns with CWE-295 which addresses improper certificate validation, and it maps to ATT&CK technique T1566 related to spearphishing attacks that leverage trust in digital signatures to bypass security controls. Organizations should also review their email security policies to ensure that users understand the risks of opening emails with multiple signatures and maintain regular security awareness training programs to address social engineering aspects of this vulnerability.