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7.8

Cisco IOS DNS over TCP can crash device

CVE-2013-5479 · published 13 years ago
Summary

Cisco IOS versions 12.2 and 15.0‑15.3 may restart unexpectedly when they handle specially crafted DNS requests over TCP while NAT is enabled. This can interrupt network services and require a manual reboot. Apply the Cisco software update that fixes the DNS handling or disable DNS over TCP if it is not needed.

What to do

The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.

Affected software
VendorProductAffected versions
cisco ios 12.2
15.0
15.1
15.2
15.3
cpe:2.3:o:cisco:ios:12.2:*:*:*:*:*:*:*
Original advisory text
The DNS-over-TCP implementation in Cisco IOS 12.2 and 15.0 through 15.3, when NAT is used, allows remote attackers to cause a denial of service (device reload) via a crafted IPv4 DNS TCP stream, ak...
The DNS-over-TCP implementation in Cisco IOS 12.2 and 15.0 through 15.3, when NAT is used, allows remote attackers to cause a denial of service (device reload) via a crafted IPv4 DNS TCP stream, aka Bug ID CSCtn53730.
References
Fix within
Internet-facing 14 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically (estimated)
  • Gives an attacker partial control (estimated)
Severity
7.8 High
Exploitation
2% chance of attack within 30 days
Type
CWE-20Improper Input Validation
Timeline
Published27 Sep 2013
Updated3 Nov 2026
First seen29 Sep 2026
Sources
CVE-2013-5479 · NVD
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