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PixHardware / appliance · Cisco

CVE-2005-3774

MEDIUM · 5.0 CVSS v2.0 Published 2005-11-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
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
Cisco PIX 6.3 and 7.0 allows remote attackers to cause a denial of service (blocked new connections) via spoofed TCP packets that cause the PIX to create embryonic connections that that would not produce a valid connection with the end system, including (1) SYN packets with invalid checksums, which do not result in a RST; or, from an external interface, (2) one byte of "meaningless data," or (3) a TTL that is one less than needed to reach the internal destination.

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

Cisco PIX 6.3 and 7.0 firewalls can be exhausted into a denial of service by remote attackers sending spoofed TCP packets that create incomplete 'embryonic connections'. These include SYN packets with invalid checksums that don't trigger a RST, single bytes of meaningless data from external interfaces, or packets with TTL set one hop short of the internal destination. The firewall maintains state for these incomplete connections until timeout, eventually blocking all new legitimate connections.

MitigationUpgrade from legacy PIX appliances to Cisco ASA (Adaptive Security Appliance) or apply available PIX software updates if still supported. Implement upstream network filtering or rate-limiting at ISP edge to drop malformed/spoofed packets before reaching the PIX.

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
PixHardware / appliance
Affected:= 6.3= 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
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial

AV:N/AC:L/Au:N/C:N/I:N/A:P

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 Cisco PIX software version
    Run 'show version' on the PIX console or via SSH/Telnet to display the operating system version and model information
    Affected if The displayed version shows 6.3(x) or 7.0(x) where x is any sub-version number
  2. Verify embryonic connection tracking is active
    Run 'show timeout' to display the embryonic connection timeout value. Default is typically 30 seconds on affected versions. Also run 'show conn' to view current connection states
    Affected if Embryonic timeout is set to a non-zero value (default 30s) and the firewall is actively tracking TCP connections - this is the default stateful inspection behavior
  3. Check for accumulated incomplete connections
    Run 'show conn' and look for connections in embryonic state (shown as ' embryonic' or incomplete TCP flags). Count the number of such entries
    Affected if The 'show conn' output shows a high number of connections stuck in embryonic or incomplete state, especially from external/interfaces
  4. Monitor connection table exhaustion
    Run 'show resource usage' or 'show memory' to check if the connection table or memory is near capacity. Also check 'show asp drop' for any embryonic connection drops
    Affected if Connection table shows maximum connections reached, memory is constrained, or asp drop shows embryonic connection accumulation indicating the DoS is active
  5. Review traffic from external interfaces for attack patterns
    Use 'show log' or 'show logging' to examine logs for patterns: packets with invalid TCP checksums, single-byte TCP data, or TTL-exceeded messages from upstream routers
    Affected if Logging reveals malformed packets as described (invalid checksums, single bytes, TTL issues) arriving on external interfaces in high volume

A Cisco PIX 6.3 or 7.0 environment with default stateful inspection enabled is affected if it shows accumulation of embryonic connections or connection table exhaustion when receiving malformed spoofed packets from external networks.

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 from legacy PIX appliances to Cisco ASA (Adaptive Security Appliance) or apply available PIX software updates if still supported. Implement upstream network filtering or rate-limiting at ISP edge to drop malformed/spoofed packets before reaching the PIX.

Fix this in Pix Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2005-3774 in production — separate from our analysis above.

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What this is

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What belongs here
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