CVE-2025-3757 in OPKSSH
Summary
by MITRE • 05/13/2025
Versions of OpenPubkey library prior to 0.10.0 contained a vulnerability that would allow a specially crafted JWS to bypass signature verification.
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Analysis
by VulDB Data Team • 05/24/2025
The vulnerability identified as CVE-2025-3757 affects the OpenPubkey library, a cryptographic library designed for public key operations and digital signatures. This issue represents a critical flaw in the library's signature verification mechanism that could potentially compromise the integrity and authenticity guarantees that digital signatures are meant to provide. The vulnerability specifically impacts versions prior to 0.10.0, indicating that the developers have acknowledged and addressed this weakness in their subsequent releases.
The technical flaw resides in the library's handling of JWS (JSON Web Signatures) where a specially crafted signature can bypass the verification process entirely. This represents a classic case of insufficient input validation and improper error handling within the cryptographic verification routine. The vulnerability allows an attacker to construct a malformed JWS payload that appears valid to the library's verification function while actually containing malicious content. This weakness stems from inadequate parsing or validation of the JWS structure, potentially allowing attackers to manipulate the signature verification flow without proper authentication.
The operational impact of this vulnerability is significant as it undermines the fundamental security assumptions of any system relying on OpenPubkey for signature verification. An attacker who can exploit this vulnerability could potentially forge digital signatures, impersonate legitimate entities, or inject malicious content into systems that trust these signatures. The implications extend beyond simple authentication bypass as this weakness could enable more sophisticated attacks such as man-in-the-middle scenarios or credential theft. Systems that depend on OpenPubkey for validating user identities, document authenticity, or API authentication could be compromised, potentially affecting thousands of applications that utilize this library.
Organizations using affected versions of OpenPubkey should immediately upgrade to version 0.10.0 or later to remediate this vulnerability. The fix likely involves strengthening the JWS parsing logic and implementing more robust signature validation checks that properly handle edge cases and malformed inputs. Security teams should conduct comprehensive audits of all systems that utilize OpenPubkey to identify potential exploitation vectors and ensure that all instances have been updated. Additionally, monitoring for suspicious signature validation patterns and implementing proper logging of verification failures can help detect potential exploitation attempts. This vulnerability aligns with CWE-295 which addresses improper certificate validation and could potentially map to ATT&CK techniques involving credential access and privilege escalation through signature manipulation. Organizations should also consider implementing additional security controls such as signature pinning, multi-factor authentication, and regular security assessments to mitigate the risk of exploitation.