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Steam Link FirmwareOperating system · Valvesoftware

CVE-2017-17877

CRITICAL · 9.8 CVSS v3.0 Published 2017-12-27
Fix available
A fix is available. Upgrade to 644 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
An issue was discovered in Valve Steam Link build 643. When the SSH daemon is enabled for local development, the device is publicly available via IPv6 TCP port 22 over the internet (with stateless address autoconfiguration) by default, which makes it easier for remote attackers to obtain access by guessing 24 bits of the MAC address and attempting a root login. This can be exploited in conjunction with CVE-2017-17878.

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

The Valve Steam Link device (build 643) enables an SSH daemon by default for local development purposes, exposing TCP port 22 to the internet via IPv6 using stateless address autoconfiguration (SLAAC). Since IPv6 addresses are derived from MAC addresses, attackers can predict the address by guessing only 24 bits of the MAC address and attempt root login, achieving remote code execution.

MitigationDisable the SSH daemon if not required for development; otherwise, implement IPv6 firewall rules to block external port 22 access, disable root login, and enforce key-based authentication.

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
Steam Link FirmwareOperating system
Affected:< 644

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 Steam Link device on network
    Scan the network for devices with Steam Link manufacturer OUI (VALVE or related) or identify the device via its hostname or mDNS/UPnP service announcements
    Affected if The device is directly accessible from the internet via IPv6 without firewall protection
  2. Check firmware version
    Access the Steam Link device settings UI or check via network enumeration tools for the firmware build number
    Affected if The firmware version is build 643 or any version below 644
  3. Verify SSH daemon is exposed on IPv6
    Attempt to connect to TCP port 22 using the device's IPv6 address (derived from MAC address via SLAAC) from an external network
    Affected if Port 22 responds to IPv6 connections from untrusted networks
  4. Confirm SSH root login is permitted
    If SSH access is obtained, attempt to log in as root user or check SSH daemon configuration for PermitRootLogin setting
    Affected if Root login is allowed without key-based authentication enforced

A user is affected if they have a Steam Link running firmware below build 644 with SSH enabled and accessible via IPv6 from untrusted networks, especially with root login permitted.

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 644 or later
Fixed in 644
Interim mitigation

Disable the SSH daemon if not required for development; otherwise, implement IPv6 firewall rules to block external port 22 access, disable root login, and enforce key-based authentication.

Recommended fix High confidence

Steam Link Firmware 644 or later

  1. Ensure your Steam Link device is connected to your network and powered on
  2. On your Steam-linked PC, open Steam and navigate to the Steam Link settings (Steam > Settings > Steam Link)
  3. Select the Steam Link device and choose 'Update Firmware' or check for available updates
  4. If an update is available, allow the firmware to update to version 644 or later
  5. After the update completes, verify the firmware version in the Steam Link settings
  6. As a security best practice after updating, consider disabling SSH in the Steam Link settings if you do not need local development access

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

Fix this in Steam Link Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,820
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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-2017-17877 in production — separate from our analysis above.

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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