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Debian LinuxOperating system · Debian

CVE-2016-1908

CRITICAL · 9.8 CVSS v3.1 Published 2017-04-11
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The client in OpenSSH before 7.2 mishandles failed cookie generation for untrusted X11 forwarding and relies on the local X11 server for access-control decisions, which allows remote X11 clients to trigger a fallback and obtain trusted X11 forwarding privileges by leveraging configuration issues on this X11 server, as demonstrated by lack of the SECURITY extension on this X11 server.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-287

The mechanism that verifies who a user is can be side-stepped or fooled, letting an attacker act as someone they're not. Everything built on top of that identity then becomes untrustworthy. Fixing it means hardening the full authentication flow, including edge cases, tokens, and secondary paths.

General guidance for the improper authentication class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 8.0
LinuxOperating system
Affected:= 6= 7
Enterprise Linux DesktopOperating system
Affected:= 6.0= 7.0
Enterprise Linux EusOperating system
Affected:= 7.2= 7.3= 7.4= 7.5= 7.6= 7.7
Enterprise Linux ServerOperating system
Affected:= 6.0= 7.0
Enterprise Linux Server AusOperating system
Affected:= 7.2= 7.3= 7.4= 7.6= 7.7
Enterprise Linux Server TusOperating system
Affected:= 7.2= 7.3= 7.6= 7.7
Enterprise Linux WorkstationOperating system
Affected:= 6.0= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch anongit.mindrot.org →
Recommended fix High confidence

OpenSSH 7.2 or later

  1. Check current OpenSSH version with: ssh -V or dpkg -l | grep openssh or rpm -q openssh
  2. Upgrade OpenSSH client and server packages. On RHEL/CentOS systems: yum update openssh openssh-clients openssh-server
  3. On Debian systems: apt-get update && apt-get install openssh-client openssh-server
  4. Restart the SSH service after upgrade: systemctl restart sshd (or service ssh restart)
  5. Verify the installed version is 7.2 or later: ssh -V
Caveat OpenSSH 7.2 introduced several changes including deprecation of certain cipher suites; review release notes for compatibility with existing infrastructure

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-1908 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data