In Paramiko through 4.0.0 before a448945, rsakey.py allows the SHA-1 algorithm.

https://ostif.org/paramiko-audit-complete/ announces: The Open Source Technology Improvement Fund is proud to share the results of our security audit of Paramiko. Paramiko is an open source Python implementation of the SSHv2 protocol designed for secure remote login and other secure network services. Thanks to the help of Quarkslab and Alpha-Omega, this project received custom security work reviewing Paramiko’s testing, building and CI systems, and cryptography.

Audit Process:

The engagement took place in November 2025, with Quarkslab’s audit team executing the mission on Paramiko’s testing, building, and CI systems. In order to effectively execute this work on critical security features of Paramiko, the scope was expanded to include PYCA Cryptography and how it interacts with Paramiko critical cryptographic functions, (PYCA) Cryptography’s OpenSSL Rust Bindings, and CI/CD CircleCI for Paramiko and Github Actions for (PYCA) Cryptography. For Paramiko the engagement consisted of manual code review, dependencies review, dynamic testing, build systems, testing enhancements, static analysis, and fuzz testing.

Audit Results:

30 Findings with Security Impact - 2 High - 7 Medium - 5 Low - 16 Informational Build and CI/CD Pipeline Review Testing Enhancements - Implementation of a crypto-condor plug-in to incorporate in the CI for cryptographic compliance and testing of entropy sources - Review of current testing coverage SSH RFC compliance review

The project maintainer worked diligently to address and resolve the issues presented by this report, engaging with the audit team to design fix solutions aligned with security best practices. Update to the most recent release of Paramiko (version 5.0 will release early May 2026) and follow documentation in order to take advantage of the hard work of the individuals behind Paramiko and Quarkslab. If you’re interested in contributing to Paramiko, learn more about them and their community on their website: https://www.paramiko.org/ .

Thank you to the individuals and groups that made this engagement possible:

Paramiko maintainers and community, especially: Jeff Forcier Quarkslab: Dahmun Goudarzi, Julio Loayza Meneses, Alan Marrec, and Pauline Sauder Alpha-Omega

You can read the Audit Report at https://ostif.org/wp-content/uploads/2026/05/25-11-2415-REPparamiko-security-auditv1.1.pdf

Everyone around the world depends on open source software. If you’re interested in financially supporting this critical work, reach out to contactus () ostif org. The findings listed in the audit report at higher than "Informational" are: HIGH-21 Insecure parameters for digital signatures with RSA HIGH-28 Insecure key sizes accepted for Triple DES [in Cryptography] MEDIUM-15 Deprecated group exchange method MEDIUM-16 Insecure minimum modulus size in Diffie-Hellman group exchange MEDIUM-17 Deprecated Diffie-Hellman group MEDIUM-18 Deprecated GSS-API key exchange methods MEDIUM-22 Use of 8-byte seed for TripleDES key generation MEDIUM-24 Wrong type usage in SHA-1 in KexGSSGroup1 and KexGSSGroup14 LOW-27 Invalid Ed25519 signature cause transport thread to crash LOW-29 Insecure RSA key size allowed RSA Keys in Paramiko and Cryptography LOW-30 Server can be instantiated over UDP socket with these recommendations to resolve them: HIGH-21 Remove support for RSA with SHA-1. HIGH-28 Reject key sizes that are not 24 bytes. MEDIUM-15 Remove support for diffie-hellman-group-exchange-sha1. MEDIUM-16 Increase the minimum modulus size to 2048 bits. MEDIUM-17 Remove support for diffie-hellman-group1-sha1. MEDIUM-18 Remove the deprecated key exchange methods, replacing them with RFC 8732 additions. MEDIUM-22 Reject 8-byte input for the key initialization of Triple DES. MEDIUM-24 Change str(hm) to hm.asbytes() in KexGSSGroup1. LOW-1 Update black to version 24.3.0. LOW-19 Warn when using this format, recommend the user to save their keys in PKCS8 or OpenSSH format instead. LOW-25 Either check the length of the signature before calling verify() or handle the exception. LOW-27 Handle the exception: either catch the nacl.exception.ValueError excep- tion or check that the signature has the correct length before calling verify(). LOW-29 Reject RSA keys that are shorter than 2048 bits. LOW-30 Add a check in Transport.init() to verify that sock is a TCP socket. -- -Alan Coopersmith- alan.coopersmith () oracle com Oracle Solaris Engineering - https://blogs.oracle.com/solaris

USN-3796-1 fixed a vulnerability in Paramiko. This update provides the corresponding update for Ubuntu 18.10. Original advisory details: Daniel Hoffman discovered that Paramiko incorrectly handled authentication when being used as a server. A remote attacker could use this issue to bypass authentication without any credentials.