dbcve.org
FedoraOperating system · Fedoraproject

CVE-2019-9895

CRITICAL · 9.8 CVSS v3.0 Published 2019-03-21
Fix available
A fix is available. Upgrade to 0.71 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
In PuTTY versions before 0.71 on Unix, a remotely triggerable buffer overflow exists in any kind of server-to-client forwarding.

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 · high confidence

A remotely triggerable buffer overflow vulnerability exists in PuTTY versions prior to 0.71 on Unix platforms. The flaw resides in the server-to-client forwarding functionality (likely in the SSH channel handling code), allowing a malicious SSH server to overflow a buffer by sending specially crafted data during port forwarding operations, potentially leading to arbitrary code execution on the client.

MitigationUpgrade PuTTY on all Unix/Linux clients to version 0.71 or later. Since this is a client-side vulnerability, ensure all users running vulnerable PuTTY versions apply the update promptly.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
FedoraOperating system
Affected:= 28= 29
PuttyApplication
Affected:< 0.71

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if PuTTY is installed
    Run 'which putty' or 'dpkg -l | grep putty' (Debian/Ubuntu) or 'rpm -qa | grep putty' (RHEL/Fedora) to check for PuTTY packages
    Affected if PuTTY is not installed means not affected; if installed, proceed to version check
  2. Determine installed PuTTY version
    Run 'putty --version' or 'puttygen --version' to display the version number
    Affected if Version is less than 0.71 (for example, 0.70, 0.68, etc.) indicates vulnerability
  3. Verify operating system platform
    Check OS with 'uname -a' or 'cat /etc/os-release'; this vulnerability affects Unix/Linux platforms only
    Affected if Running on Unix/Linux (Fedora, Linux, BSD, etc.) with vulnerable PuTTY version means affected
  4. Confirm port forwarding usage
    Review PuTTY configuration for enabled SSH port forwarding features (Local or Remote port forwarding) in saved sessions or active connections
    Affected if Port forwarding is enabled and the client connects to SSH servers (including potentially untrusted ones)

A user is affected if they run PuTTY versions prior to 0.71 on Unix/Linux platforms and use SSH port forwarding to connect to SSH servers, as the buffer overflow can be triggered by a malicious server sending crafted forwarding data.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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
Upgrade available Upgrade to 0.71 or later
Fixed in 0.71
Interim mitigation

Upgrade PuTTY on all Unix/Linux clients to version 0.71 or later. Since this is a client-side vulnerability, ensure all users running vulnerable PuTTY versions apply the update promptly.

Recommended fix High confidence

PuTTY 0.71 or later

  1. 1. Check the currently installed PuTTY version by running: putty --version
  2. 2. For systems using package managers, update PuTTY to version 0.71 or later:
  3. - On Fedora: sudo dnf update putty
  4. - On Debian/Ubuntu: sudo apt-get update && sudo apt-get install putty
  5. - On openSUSE: sudo zypper update putty
  6. 3. If installing from source, download PuTTY 0.71 or later from the official site: https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
  7. 4. Verify the new version is installed correctly: putty --version
  8. 5. Restart any running PuTTY sessions to ensure the updated version is used

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

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

Scan for this in your stack

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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-2019-9895 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