Description
The auth_password function in auth-passwd.c in sshd in OpenSSH before 7.3 does not limit password lengths for password authentication, which allows remote attackers to cause a denial of service (crypt CPU consumption) via a long string.
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 | 1:7.3p1-1 | — |
| Debian 13 | openssh | 1:7.3p1-1 | — |
| Debian 12 | openssh | 1:7.3p1-1 | — |
| Debian 8 | openssh | 1:6.7p1-5+deb8u6 | DLA-1500-1 |
| Debian 7 | openssh | 1:6.0p1-4+deb7u6 | DLA-594-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | openssh | 1:7.2p2-4ubuntu2.1 | USN-3061-1 |
| Ubuntu 14.04 LTS | openssh | 1:6.6p1-2ubuntu2.8 | USN-3061-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | openssh +7 | 7.4p1-11.el7 | RHSA-2017:2029 |
| RHEL 7 | pam_ssh_agent_auth | 0.10.3-1.11.el7 | RHSA-2017:2029 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP1 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES 12 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES 11 SP4 | openssh | 6.6p1-28.1 | SUSE-SU-2016:2281-1 |
| SLES 11 SP4 | openssh-askpass-gnome | 6.6p1-28.2 | SUSE-SU-2016:2281-1 |
| SLES 11 SP3 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SLES 11 SP3 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SLES 11 | openssh-openssl1 | 6.6p1-15.1 | SUSE-SU-2016:2555-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP1 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES for SAP 12 | openssh +1 | 6.6p1-52.1 | SUSE-SU-2016:2280-1 |
| SLES for SAP 11 SP4 | openssh | 6.6p1-28.1 | SUSE-SU-2016:2281-1 |
| SLES for SAP 11 SP4 | openssh-askpass-gnome | 6.6p1-28.2 | SUSE-SU-2016:2281-1 |
| SUSE OpenStack Cloud 5 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE OpenStack Cloud 5 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Manager Proxy 2.1 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Manager Proxy 2.1 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Manager 2.1 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Manager 2.1 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | openssh | 6.2p2-0.33.2 | SUSE-SU-2016:2388-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | openssh-askpass-gnome | 6.2p2-0.33.5 | SUSE-SU-2016:2388-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | openssh | 7.2p2-3.1 | openSUSE-SU-2024:10174-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.4 | openssh | 7.2_p2-r2 | — |
| Alpine v3.3 | openssh | 7.2_p2-r2 | — |
| Alpine v3.2 | openssh | 6.8_p1-r8 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | openssh +7 | 7.4p1-11.el7 | ELSA-2017-2029 |
| Oracle Linux 7 | pam_ssh_agent_auth | 0.10.3-1.11.el7 | ELSA-2017-2029 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- OpenSSH 7.2 - Denial of Service EDB-40888 · dos · Dec 7, 2016
GitHub 3 repositories
-
opsxcq/exploit-CVE-2016-6515 ★ 53 · Dec 9, 2016
OpenSSH remote DOS exploit and vulnerable container
-
jptr218/openssh_dos ★ 1 · Aug 26, 2021
A proof of concept for CVE-2016-6515
-
cved-sources/cve-2016-6515 ★ 0 · Jan 6, 2019
cve-2016-6515
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 14
- RHSA-2017:2029 Red Hat Security Advisory: openssh security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-3061-1 openssh vulnerabilities Ubuntu Security Notices (USN) · Jun 1, 2026
- DLA-594-1 openssh - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1500-1 openssh - security update Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2024:10174-1 openssh-7.2p2-3.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2281-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2555-1 Security update for openssh-openssl1 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2280-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2388-1 Security update for openssh SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2023-0449 OpenSSH: Mehrere Schwachstellen BSI CERT-Bund (WID) · May 7, 2024
- SSA-676336 SSA-676336: OpenSSH Vulnerabilities in SCALANCE X-200 and X-300/X408 Switches Siemens ProductCERT · Apr 11, 2023
- ICSA-22-349-21 Siemens SCALANCE X-200RNA Switch Devices CISA ICS & IT advisories · Dec 13, 2022
- SSA-412672 SSA-412672: Multiple OpenSSL and OpenSSH Vulnerabilities in SCALANCE X-200RNA Switch Devices before V3.2.7 Siemens ProductCERT · Dec 13, 2022
- ELSA-2017-2029 Moderate: openssh security, bug fix, and enhancement update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Aug 7, 2017
References
- https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03779en_us
- https://security.netapp.com/advisory/ntap-20171130-0003/
- https://github.com/openssh/openssh-portable/commit/fcd135c9df440bcd2d5870405ad3311743d78d97
- http://packetstormsecurity.com/files/140070/OpenSSH-7.2-Denial-Of-Service.html
- 40888 exploit
- 92212 vdb-entry
- FreeBSD-SA-17:06 vendor-advisory
- http://www.oracle.com/technetwork/security-advisory/cpuoct2017-3236626.html
- 1036487 vdb-entry
- FEDORA-2016-4a3debc3a6 vendor-advisory
- RHSA-2017:2029 vendor-advisory
- [debian-lts-announce] 20180910 [SECURITY] [DLA 1500-1] openssh security update mailing-list
- [oss-security] 20160801 Announce: OpenSSH 7.3 released mailing-list
- https://cert-portal.siemens.com/productcert/pdf/ssa-676336.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf