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Dpc3939 FirmwareOperating system · Cisco

CVE-2017-9491

MEDIUM · 5.3 CVSS v3.1 Published 2017-07-31
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
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
The Comcast firmware on Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421733-160420a-CMCST); Cisco DPC3939 (firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST); Cisco DPC3939B (firmware version dpc3939b-v303r204217-150321a-CMCST); Cisco DPC3941T (firmware version DPC3941_2.5s3_PROD_sey); and Arris TG1682G (eMTA&DOCSIS version 10.0.132.SIP.PC20.CT, software version TG1682_2.2p7s2_PROD_sey) devices does not set the secure flag for cookies in an https session to an administration application, which makes it easier for remote attackers to capture these cookies by intercepting their transmission within an http session.

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

Multiple Comcast-provided gateway devices (Cisco DPC3939, DPC3939B, DPC3941T, and Arris TG1682G) fail to set the Secure flag on session cookies even when the administration interface is accessed via HTTPS, allowing cookies to be transmitted over insecure connections and vulnerable to interception.

MitigationThe device firmware must be updated to set the Secure attribute on all session cookies, ensuring they are only transmitted over encrypted HTTPS connections. Users should also ensure they access the admin interface only over trusted networks.

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
Dpc3939 FirmwareOperating system
Affected:= dpc3939-p20-18-v303r20421733-160420a-cmcst= dpc3939-p20-18-v303r20421746-170221a-cmcst
Dpc3939b FirmwareOperating system
Affected:= dpc3939b-v303r204217-150321a-cmcst
Dpc3941t FirmwareOperating system
Affected:= dpc3941_2.5s3_prod_sey
Arris Tg1682g FirmwareOperating system
Affected:= 10.0.132.sip.pc20.ct= tg1682_2.2p7s2_prod_sey

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
Low
Integrity
None
Availability
None

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

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 your gateway device model
    Locate the device label on your gateway or access the admin interface (typically at 192.168.0.1 or 192.168.1.1) and check the device information page to confirm the exact model number (DPC3939, DPC3939B, DPC3941T, or TG1682G)
    Affected if The device model is one of: Cisco DPC3939, Cisco DPC3939B, Cisco DPC3941T, or Arris TG1682G
  2. Check the installed firmware version
    In the gateway admin interface, navigate to the Status, Diagnostics, or Firmware version section to find the exact firmware string installed on your device
    Affected if The firmware version matches exactly one of: dpc3939-p20-18-v303r20421733-160420a-cmcst, dpc3939-p20-18-v303r20421746-170221a-cmcst, dpc3939b-v303r204217-150321a-cmcst, dpc3941_2.5s3_prod_sey, 10.0.132.sip.pc20.ct, or tg1682_2.2p7s2_prod_sey
  3. Verify if the Secure flag is set on session cookies
    Using browser developer tools (F12), access your gateway admin interface over HTTPS, then inspect the session cookies in the Application or Storage tab. Check the cookie attributes for the presence of the Secure flag
    Affected if The session cookies do NOT have the Secure flag set, meaning they can be transmitted over insecure HTTP connections despite HTTPS access

You are affected if your gateway is one of the four listed models AND your firmware version matches one of the six specific versions AND your session cookies are missing the Secure attribute.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

The device firmware must be updated to set the Secure attribute on all session cookies, ensuring they are only transmitted over encrypted HTTPS connections. Users should also ensure they access the admin interface only over trusted networks.

Fix this in Dpc3939 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing3.0 h
  • Review / QA2.0 h
17.0 hours of engineering $3,050
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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-2017-9491 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