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Vulnerability Intelligence

CVE-2016-6515

HighPublic exploit

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.

Published Aug 7, 2016 · Updated Aug 4, 2026 · Also known as ALPINE-CVE-2016-6515, DEBIAN-CVE-2016-6515, DLA-594-1, UBUNTU-CVE-2016-6515

Key Facts

Patch immediately
  • CVE-2016-6515 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting Openssh (Openbsd), Fedora (Fedoraproject), rootio-openssh and 13 more products.
  • It is not listed in any known-exploited vulnerabilities catalog. Public exploit code is available.
  • EPSS estimates a 59% probability of exploitation in the next 30 days.
  • Fixed versions are available, including Openssh 7.2, Openssh 0:7.4p1-11.el7, Openssh 1:6.0p1-4+deb7u6.
  • Brandefense priority: patch immediately, because it is very likely to be exploited soon.

CVSS v3.1

7.5

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS (30-day exploit likelihood)

59%

Higher than 99.0% of all scored CVEs

Exploited in the wild

No known

Not in a known-exploited catalog

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2016-6515 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

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.

Affected Products

124 affected entries in total
ProductAffected versionsFixed in
OpensshOpenbsdSee advisory7.2
FedoraFedoraproject24n/a
rootio-opensshrootioSee advisory1:7.3p1-1
openssh-cavsamazonSee advisory7.4p1-11.68.amzn1
openssh-clientsamazonSee advisory7.4p1-11.68.amzn1
11 more affected products in the full CVE brief

Patched Releases

Openssh

7.2, 0:7.4p1-11.el7, 1:6.0p1-4+deb7u6, 1:6.6p1-2ubuntu2.8, 1:6.7p1-5+deb8u6, 1:7.2p2-4ubuntu2.1, 1:7.3p1-1, 6.2p2-0.33.2, 6.6p1-14.1, 6.6p1-28.1, 6.6p1-52.1, 6.8_p1-r8, 7.2_p2-r2, 7.2p2-3.1, 7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-askpass

6.2p2-0.33.2, 7.4p1-11.el7

openssh-askpass-gnome

6.2p2-0.33.5, 6.6p1-14.1, 6.6p1-28.2, 6.6p1-52.1

openssh-cavs

6.6p1-14.1, 7.2p2-3.1, 7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-clients

7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-fips

6.6p1-14.1, 6.6p1-28.1, 6.6p1-52.1, 7.2p2-3.1

openssh-helpers

6.6p1-14.1, 6.6p1-28.1, 6.6p1-52.1, 7.2p2-3.1

openssh-keycat

7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-ldap

7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-openssl1

6.6p1-15.1

openssh-openssl1-helpers

6.6p1-15.1

openssh-server

7.4p1-11.68.amzn1, 7.4p1-11.el7

openssh-server-sysvinit

7.4p1-11.el7

pam_ssh_agent_auth

0.10.3-1.11.68.amzn1, 0.10.3-1.11.el7

rootio-openssh

1:7.3p1-1

Timeline

  1. Publicly disclosed

    Aug 7, 2016

  2. Last updated

    Aug 4, 2026

Weakness Type

  • CWE-20 Improper Input Validation
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

15 more references in the full CVE brief

FAQ

Common Questions.

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