Vulnerability record · CVE-2016-0777 · published 14 January 2016
CVE-2016-0777: OpenSSH client memory disclosure via roaming resend_bytes
Sophos · Unified Threat Management Software
The resend_bytes function in the OpenSSH client's roaming_common.c mishandles buffer resend requests, allowing a malicious or compromised SSH server to read process memory from the connecting client. Because the leaked memory can include the client's private key material, this undermines the confidentiality of credentials used for authentication.
Description
The resend_bytes function in roaming_common.c in the client in OpenSSH 5.x, 6.x, and 7.x before 7.1p2 allows remote servers to obtain sensitive information from process memory by requesting transmission of an entire buffer, as demonstrated by reading a private key.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Automated analysis
high priorityThe flaw leaks private key material with a high EPSS score, though it requires connecting to a malicious server and is not known to be actively exploited.
What it is
The resend_bytes function in the OpenSSH client's roaming_common.c mishandles buffer resend requests, allowing a malicious or compromised SSH server to read process memory from the connecting client. Because the leaked memory can include the client's private key material, this undermines the confidentiality of credentials used for authentication.
Impact
An attacker controlling the SSH server can obtain sensitive client process memory, including private keys, enabling impersonation of the victim against other systems that trust those keys.
Attack surface
Reached over the network when a client connects to a malicious or compromised SSH server; no user interaction beyond initiating the connection is required, and the CVSS vector indicates low privileges (PR:L) with no UI.
Exploitation
Not listed in CISA KEV and no ransomware associations are documented, but EPSS is high at 0.635 (99.2nd percentile), and references are advisories and vendor bulletins rather than exploit code.
What to do
- Upgrade OpenSSH clients to 7.1p2 or later, or apply the vendor patch for your distribution.
- Disable roaming in the client configuration (UseRoaming no) as a workaround where patching is delayed.
- Rotate any SSH private keys that may have been used from unpatched clients connecting to untrusted servers.
- Inventory OpenSSH client versions across managed endpoints and embedded products (UTM, macOS, Solaris, Linux) and prioritize those still below 7.1p2.
Detection
- Monitor SSH client connections to untrusted or external servers from hosts running OpenSSH versions below 7.1p2.
- Audit client configurations for UseRoaming settings and flag hosts where roaming is enabled.
- Review authentication logs for unexpected key-based logins that could indicate a leaked private key being reused.
This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.
Affected products
6 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
Track CVE-2016-0777 inside VULONE
Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.
Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2016-0777), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
