Exploited CVE from 2004, added in 2023

CVE-2004-1464

Cisco IOS / IOS XE · Switches, routers and SD-WAN

Cisco IOS Denial-of-Service Vulnerability

At a glance

Exploited. Added to CISA’s catalog of exploited vulnerabilities on May 19, 2023.

Affected product: Cisco IOS / IOS XE (category Switches, routers and SD-WAN, indicative classification). Name in CISA’s catalog: Cisco IOS.

What should I do?

Apply the security update from Cisco.

Deadline set by CISA for US federal agencies: 21 days (due June 9, 2023). It only binds those agencies, but it is a useful measure of urgency.

Cisco security advisories page (general page, not the advisory for this vulnerability)
The vendor’s specific advisory is listed in the NVD references: CVE-2004-1464 on the NVD website.

Original text of the required action (CISA)

Apply updates per vendor instructions.

Timeline

December 31, 2004 Vulnerability published Publication date (NVD)
May 19, 2023 Exploitation confirmed Added to CISA’s KEV catalog
June 9, 2023 CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Exploitation confirmed: Yes, on May 19, 2023 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Ransomware: No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Hunt for compromise: Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA required action: Apply the security update from Cisco. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA deadline: June 9, 2023, 21 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Vulnerability published: December 31, 2004 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Product according to CISA: Cisco IOS Filed by this site under “Switches, routers and SD-WAN” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC

Severity and activity

5.9 / 10 CVSS severity: medium

Score from the NVD. Collected Sep 29, 2026.

— Probability of exploitation in the next 30 days (EPSS)

FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.

Description

Cisco IOS 12.2(15) and earlier allows remote attackers to cause a denial of service (refused VTY (virtual terminal) connections), via a crafted TCP connection to the Telnet or reverse Telnet port.

Cisco IOS contains an unspecified vulnerability that may block further telnet, reverse telnet, Remote Shell (RSH), Secure Shell (SSH), and in some cases, Hypertext Transport Protocol (HTTP) access to the Cisco device.

Summary from CISA (KEV catalog).

CERT-FR advisories

No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page

CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
NVD (NIST): CVSS severity, publication date, description, vendor references.
EPSS (FIRST): probability of exploitation.
CERT-FR: advisories and alerts (in French).
Brand and category: indicative classification by this site (method).