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Snort\+\+Application · Cisco

CVE-2017-6657

HIGH · 7.5 CVSS v3.0 Published 2017-05-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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
Cisco Sourcefire Snort 3.0 before build 233 mishandles Ether Type Validation. Since valid ether type and IP protocol numbers do not overlap, Snort++ stores all protocol decoders in a single array. That makes it possible to craft packets that have IP protocol numbers in the ether type field which will confuse the Snort++ decoder. For example, an eth:llc:snap:icmp6 packet will cause a crash because there is no ip6 header with which to calculate the icmp6 checksum. Affected decoders include gre, llc, trans_bridge, ciscometadata, linux_sll, and token_ring. The fix adds a check in the packet manager to validate the ether type before indexing the decoder array. An out of range ether type will raise 116:473.

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

In Cisco Sourcefire Snort 3.0 before build 233, the Snort++ decoder stores all protocol decoders in a single array, assuming ether types and IP protocol numbers don't overlap. Attackers can craft packets with IP protocol numbers in the ether type field (e.g., eth:llc:snap:icmp6), which confuses the decoder and causes a crash due to missing ip6 header for checksum calculation. Affected decoders include gre, llc, trans_bridge, ciscometadata, linux_sll, and token_ring.

MitigationUpgrade to Snort 3.0 build 233 or later, which adds ether type validation in the packet manager before indexing the decoder array (raises alert 116:473 for out-of-range ether types).

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
Snort\+\+Application
Affected:all versions

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
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Snort version and build number
    Run `snort --version` or check the Snort startup banner/logs to find the exact build number. Snort 3.0 builds before 233 are vulnerable.
    Affected if The installed Snort 3.0 version is before build 233
  2. Confirm Snort is actively decoding traffic
    Verify Snort is running in inline or passive mode and actively processing network packets. The vulnerability触发s during packet decoding, so idle installations are not at risk.
    Affected if Snort is actively processing live network traffic with vulnerable decoders enabled
  3. Check for crash logs or alerts related to decoder failures
    Review Snort alert logs and system logs (such as /var/log/snort/ or /var/log/messages) for any sudden Snort process crashes, especially when processing unusual packet types.
    Affected if Snort has crashed or generated decoder-related alerts (such as alert 116:473) without an obvious cause
  4. Determine if vulnerable decoder types are in use
    Check if your network traffic involves any of the affected decoder types: gre, llc, trans_bridge, ciscometadata, linux_sll, or token_ring. These can be identified in Snort configuration or by the types of packets seen on the monitored network.
    Affected if The monitored network traffic includes packet types that use the vulnerable decoders (gre, llc, trans_bridge, ciscometadata, linux_sll, token_ring)

A system is affected if it runs Snort 3.0 before build 233 and actively decodes network traffic that could include the vulnerable decoder types (gre, llc, trans_bridge, ciscometadata, linux_sll, or token_ring).

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

Upgrade to Snort 3.0 build 233 or later, which adds ether type validation in the packet manager before indexing the decoder array (raises alert 116:473 for out-of-range ether types).

Fix this in Snort\+\+ Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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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-2017-6657 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
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  • Version or environment caveats, and links to real fixes
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