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iOSOperating system · Cisco

CVE-2008-2739

HIGH · 7.8 CVSS v2.0 Published 2008-09-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
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
The SERVICE.DNS signature engine in the Intrusion Prevention System (IPS) in Cisco IOS 12.3 and 12.4 allows remote attackers to cause a denial of service (device crash or hang) via network traffic that triggers unspecified IPS signatures, a different vulnerability than CVE-2008-1447.

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 · moderate confidence

The SERVICE.DNS signature engine in Cisco IOS IPS (versions 12.3 and 12.4) contains a vulnerability where specially crafted network traffic targeting specific DNS-related IPS signatures can cause the device to crash or hang, resulting in denial of service.

MitigationUpgrade to a patched Cisco IOS version. Alternatively, consider disabling or tuning the SERVICE.DNS signature engine in IPS until the update can be applied.

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
iOSOperating system
Affected:= 12.3t= 12.3xl= 12.3xq= 12.3xr= 12.3xs= 12.3xx= 12.3ya= 12.3yd= 12.3yg= 12.3yh= 12.3yi= 12.3yk

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
Complete

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

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 the Cisco IOS version
    Execute 'show version' on the device CLI and locate the IOS version string in the output
    Affected if The version begins with 12.3 or 12.4 (particularly 12.3t, 12.3xl, 12.3xq, 12.3xr, 12.3xs, 12.3xx, 12.3ya, 12.3yd, 12.3yg, 12.3yh, 12.3yi, 12.3yk or any 12.4 release)
  2. Confirm IOS IPS is enabled
    Execute 'show ip ips' or 'show run | include ips' to check if Intrusion Prevention System signatures are active on the device
    Affected if IPS is configured and signatures are enabled on one or more interfaces
  3. Verify SERVICE.DNS signature engine is loaded
    Execute 'show ip ips signature' or 'show ip ips configuration' to list loaded signature engines and check if SERVICE.DNS is present and active
    Affected if The SERVICE.DNS signature engine is loaded and enabled in the IPS configuration
  4. Check for DNS-related IPS signatures
    Execute 'show ip ips signature id' commands or review signature configuration files to identify signatures in the DNS category that are enabled
    Affected if Any DNS-related signatures from the SERVICE.DNS engine are enabled and active on the device

The device is affected if it runs a vulnerable IOS 12.3/12.4 version with IOS IPS enabled and the SERVICE.DNS signature engine active with DNS-related signatures loaded.

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 a patched Cisco IOS version. Alternatively, consider disabling or tuning the SERVICE.DNS signature engine in IPS until the update can be applied.

Fix this in iOS Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2008-2739 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
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  • Version or environment caveats, and links to real fixes
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