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CVE-2009-0635

19
FAUCET Score

CVE-2009-0635 describes a memory leak vulnerability in the Cisco Tunneling Control Protocol (cTCP) encapsulation feature within Cisco IOS 12.4, specifically when an Easy VPN server is enabled. This flaw allows remote attackers to trigger a denial of service through memory exhaustion and device crashes by sending a sequence of TCP packets. With a CVSS score of 7.1, it is considered highly severe due to its remote attack vector, medium complexity, and complete availability impact. There is no evidence of active exploitation, publicly available exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
12.4tCPE matchmatch criteria
cpe:2.3:o:cisco:ios:12.4t:*:*:*:*:*:*:*
12.4xzCPE matchmatch criteria
cpe:2.3:o:cisco:ios:12.4xz:*:*:*:*:*:*:*
12.4yaCPE matchmatch criteria
cpe:2.3:o:cisco:ios:12.4ya:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

7.1HIGH

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

Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
COMPLETE
Access Vector
NETWORK
Access Complexity
MEDIUM
Authentication
NONE
Exploitability Score
8.6
Impact Score
6.9
CvssVersion
2.0

Exploit Intelligence

EPSS Score
2.51%
Probability of exploitation in next 30 days
EPSS Percentile
83.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0251 is in the 40th percentile among its peer group of 8,920 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

secunia.com / advisories/34438
Vendor Advisory
exchange.xforce.ibmcloud.com / vulnerabilities/49417
cisco.com / en/US/products/products_security_advisory09186a0080a90459.shtml
PatchVendor Advisory
cisco.com / en/US/products/products_security_advisory09186a0080a90469.shtml
PatchVendor Advisory
securityfocus.com / bid/34246
securitytracker.com / id
vupen.com / english/advisories/2009/0851
Vendor Advisory