Description
The default configuration of OpenSSH through 6.1 enforces a fixed time limit between establishing a TCP connection and completing a login, which makes it easier for remote attackers to cause a denial of service (connection-slot exhaustion) by periodically making many new TCP connections.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | openssh | 1:6.0p1-4 | — |
| Debian 13 | openssh | 1:6.0p1-4 | — |
| Debian 12 | openssh | 1:6.0p1-4 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 6 | openssh +4 | 5.3p1-94.el6 | RHSA-2013:1591 |
| RHEL 6 | pam_ssh_agent_auth | 0.9.3-94.el6 | RHSA-2013:1591 |
| RHEL 6 | rhev-hypervisor6 | 6.5-20131115.0.3.2.el6_5 | RHSA-2013:1527 |
Advisories 2
- RHSA-2013:1527 Red Hat Security Advisory: rhev-hypervisor6 security and bug fix update Red Hat Security Advisories (RHSA) · Jun 28, 2026
- RHSA-2013:1591 Red Hat Security Advisory: openssh security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 26, 2026
References
- http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/servconf.c?r1=1.234#rev1.234
- RHSA-2013:1591 vendor-advisory
- HPSBMU03409 vendor-advisory
- http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshd_config?r1=1.89#rev1.89
- https://bugzilla.redhat.com/show_bug.cgi?id=908707
- 58162 vdb-entry
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html
- http://www.oracle.com/technetwork/topics/security/cpujan2015-1972971.html
- http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshd_config.5?r1=1.156#rev1.156
- [oss-security] 20130206 Re: CVE id request: openssh? mailing-list
- oval:org.mitre.oval:def:19595 vdb-entry signature
- oval:org.mitre.oval:def:19515 vdb-entry signature