Back
CVE-2009-0635
Memory leak in the Cisco Tunneling Control Protocol (cTCP) encapsulation feature in Cisco IOS 12.4, when an Easy VPN (aka EZVPN) server is…
- 7.1HighCVSS base score
- 2.5%Exploitation in 30 daysEPSS · top 15% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Memory leak in the Cisco Tunneling Control Protocol (cTCP) encapsulation feature in Cisco IOS 12.4, when an Easy VPN (aka EZVPN) server is enabled, allows remote attackers to cause a denial of service (memory consumption and device crash) via a sequence of TCP packets.
Timeline
ID reserved
By cisco
- 37 days later
· 37 days later
Published
- 15 years later
· 15 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 2.0 | High7.1 | AV:N/AC:M/Au:N/C:N/I:N/A:C |
- EPSS (exploitation in 30 days)
- 2.5% · top 15% of all CVEs (10 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.
Affected products
n/a
- affected n/a
References
7
- http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90469.shtml (opens in a new tab)x_refsource_CONFIRMx_transferred
- 20090325 Cisco IOS cTCP Denial of Service Vulnerability (opens in a new tab)vendor-advisoryx_refsource_CISCOx_transferred
- 34438 (opens in a new tab)third-party-advisoryx_refsource_SECUNIAx_transferred
- 34246 (opens in a new tab)vdb-entryx_refsource_BIDx_transferred
- ios-ctcp-dos(49417) (opens in a new tab)vdb-entryx_refsource_XFx_transferred
- 1021895 (opens in a new tab)vdb-entryx_refsource_SECTRACKx_transferred
- ADV-2009-0851 (opens in a new tab)vdb-entryx_refsource_VUPENx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2009-0638 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2009-0635)Record last updated .