Vulnerability Description
A flaw has been found in libssh in versions prior to 0.9.6. The SSH protocol keeps track of two shared secrets during the lifetime of the session. One of them is called secret_hash and the other session_id. Initially, both of them are the same, but after key re-exchange, previous session_id is kept and used as an input to new secret_hash. Historically, both of these buffers had shared length variable, which worked as long as these buffers were same. But the key re-exchange operation can also change the key exchange method, which can be based on hash of different size, eventually creating "secret_hash" of different size than the session_id has. This becomes an issue when the session_id memory is zeroed or when it is used again during second key re-exchange.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Libssh | Libssh | >= 0.9.1, < 0.9.6 |
| Redhat | Virtualization | 4.0 |
| Redhat | Enterprise Linux | 8.0 |
| Debian | Debian Linux | 10.0 |
| Fedoraproject | Fedora | 33 |
| Oracle | Mysql Workbench | <= 8.0.27 |
| Netapp | Cloud Backup | - |
Related Weaknesses (CWE)
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1978810Issue TrackingThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202312-05
- https://security.netapp.com/advisory/ntap-20211004-0003/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4965Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2022.htmlPatchThird Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1978810Issue TrackingThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202312-05
- https://security.netapp.com/advisory/ntap-20211004-0003/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4965Third Party Advisory
FAQ
What is CVE-2021-3634?
CVE-2021-3634 is a vulnerability with a CVSS score of 6.5 (MEDIUM). A flaw has been found in libssh in versions prior to 0.9.6. The SSH protocol keeps track of two shared secrets during the lifetime of the session. One of them is called secret_hash and the other sessi...
How severe is CVE-2021-3634?
CVE-2021-3634 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-3634?
Check the references section above for vendor advisories and patch information. Affected products include: Libssh Libssh, Redhat Virtualization, Redhat Enterprise Linux, Debian Debian Linux, Fedoraproject Fedora.