IOS vulnerabilitiesAnd the versions its exploited flaws hit.
IOS is made by Cisco. We track 598 published vulnerabilities listed under that exact name, across 8,443 versions. 38 of them are on the list of flaws known to be exploited, the newest added on 13 July 2026. Cisco lists newer releases under their own names, such as IOS XE, so check those pages too.
The most recent IOS flaw added to the known-exploited list is CVE-2008-4128, on 13 July 2026. We keep watching the known-exploited list.
Is IOS listed under other names? Yes.
Cisco also lists IOS under more specific names, such as IOS XE and IOS XR. Flaws listed only under those names are counted on their own pages, not here. If you run one of these, open its page for its own exploited flaws.
- IOS XE506 published vulnerabilities
- IOS XR188 published vulnerabilities
- Ios XE SD-WAN26 published vulnerabilities
- Ios Xrv 900013 published vulnerabilities
- Ios Xrv6 published vulnerabilities
- Ios Transmission Control Protocol4 published vulnerabilities
- Ios XE Rom Monitor3 published vulnerabilities
- Ios XE 3.3xo3 published vulnerabilities
- Ios XE 3.3sg3 published vulnerabilities
- Ios XE 3.4sg3 published vulnerabilities
- Ios XE 16.12 published vulnerabilities
- Ios XE 3.2ja2 published vulnerabilities
Which versions of IOS do the exploited flaws hit?
Each exploited flaw lists the versions it affects, as published by the vendor. Find your version, then patch.
- CVE-2008-4128Exploited list, 13 Jul 2026
Cisco IOS Cross-Site Request Forgery Vulnerability
12.4 - CVE-2023-20109Exploited list, 10 Oct 2023
Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write Vulnerability
12.4(22)md12.4(22)md112.4(22)md212.4(22)mda12.4(22)mda112.4(22)mda212.4(22)mda312.4(22)mda4 - CVE-2004-1464Exploited list, 19 May 2023
Cisco IOS Denial-of-Service Vulnerability
up to 12.2(15)zj3 - CVE-2016-6415Exploited list, 19 May 2023
Cisco IOS, IOS XR, and IOS XE IKEv1 Information Disclosure Vulnerability
12.2 to 12.415.0 to 15.6 - CVE-2017-6742Exploited list, 19 Apr 2023
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-3881Exploited list, 25 Mar 2022
Cisco IOS and IOS XE Remote Code Execution Vulnerability
12.2s to 15.1(3)svs - CVE-2017-12234Exploited list, 3 Mar 2022
Cisco IOS Software Common Industrial Protocol Request Denial-of-Service Vulnerability
12.4 to 15.6 - CVE-2017-12235Exploited list, 3 Mar 2022
Cisco IOS Software for Cisco Industrial Ethernet Switches PROFINET Denial-of-Service Vulnerability
12.2 to 15.6 - CVE-2017-12237Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software Internet Key Exchange Denial-of-Service Vulnerability
15.0 to 15.6 - CVE-2017-12238Exploited list, 3 Mar 2022
Cisco Catalyst 6800 Series Switches VPLS Denial-of-Service Vulnerability
15.0 to 15.4 - CVE-2017-12240Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability
12.2 to 15.6 - CVE-2017-12319Exploited list, 3 Mar 2022
Cisco IOS XE Software Ethernet Virtual Private Network Border Gateway Protocol Denial-of-Service Vulnerability
15.4(1)s - CVE-2017-6627Exploited list, 3 Mar 2022
Cisco IOS Software and Cisco IOS XE Software UDP Packet Processing Denial-of-Service Vulnerability
15.1(2)gc15.1(2)gc115.1(2)gc215.1(4)gc15.1(4)gc115.1(4)gc215.2(1)gc15.2(1)gc1 - CVE-2017-6663Exploited list, 3 Mar 2022
Cisco IOS Software and Cisco IOS XE Software Denial-of-Service Vulnerability
15.2(3a)e15.2(3a)e115.2(3m)e215.2(3m)e315.2(3m)e615.2(3m)e815.2(3)e15.2(3)e1 - CVE-2017-6736Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6737Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6738Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6739Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6740Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6743Exploited list, 3 Mar 2022
Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
12.0 to 12.415.0 to 15.6 - CVE-2017-6744Exploited list, 3 Mar 2022
Cisco IOS Software SNMP Remote Code Execution Vulnerability
12.2(33)sxi12.2(33)sxi112.2(50)se12.2(50)se112.2(50)se212.2(50)se312.2(50)se412.2(50)se5 - CVE-2018-0155Exploited list, 3 Mar 2022
Cisco Catalyst Bidirectional Forwarding Detection Denial-of-Service Vulnerability
3.6(2)e - CVE-2018-0156Exploited list, 3 Mar 2022
Cisco IOS Software and Cisco IOS XE Software Smart Install Denial-of-Service Vulnerability
15.2(2a)ja15.2(2)e4 - CVE-2018-0158Exploited list, 3 Mar 2022
Cisco IOS and XE Software Internet Key Exchange Memory Leak Vulnerability
15.5(3)s1.115.5(3)s1.215.5(3)s1.415.5(3)s1.515.5(3)s1.715.5(3)s1.815.5(3)s1.915.5(3)s1.10 - CVE-2018-0159Exploited list, 3 Mar 2022
Cisco IOS and XE Software Internet Key Exchange Version 1 Denial-of-Service Vulnerability
15.3(3)s - CVE-2018-0161Exploited list, 3 Mar 2022
Cisco IOS Software Resource Management Errors Vulnerability
15.2(5)e - CVE-2018-0167Exploited list, 3 Mar 2022
Cisco IOS, XR, and XE Software Buffer Overflow Vulnerability
up to 15.6.3m1up to 15.2(6)e0aup to 15.2(4a)ea5 - CVE-2017-12231Exploited list, 3 Mar 2022
Cisco IOS Software Network Address Translation Denial-of-Service Vulnerability
12.4 to 15.6 - CVE-2017-12233Exploited list, 3 Mar 2022
Cisco IOS Software Common Industrial Protocol Request Denial-of-Service Vulnerability
12.4 to 15.6
1 more exploited flaw names IOS without a version of its own, for example as the system other affected software runs on. It is in the list below.
Showing the 30 most recently added of 38 exploited flaws. The full list is below.
Which IOS vulnerabilities are being exploited?
38 flaws are on the government list of vulnerabilities known to be exploited. These are the ones criminals are using now, so they go first, whatever their severity score says.
- 8.1Cisco IOS Cross-Site Request Forgery Vulnerability
Cisco IOS 12.4 contains multiple cross-site forgery vulnerabilities that allows remote attackers to execute arbitrary commands via (1) a certain "show privilege" command to the /level/15/exec/- URI, and (2) a certain...
- 6.6Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write Vulnerability
Cisco IOS and IOS XE contain an out-of-bounds write vulnerability in the Group Encrypted Transport VPN (GET VPN) feature that could allow an authenticated, remote attacker who has administrative control of either a...
- 5.9Cisco IOS Denial-of-Service Vulnerability
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.
- 7.5Cisco IOS, IOS XR, and IOS XE IKEv1 Information Disclosure Vulnerability
Cisco IOS, IOS XR, and IOS XE contain insufficient condition checks in the part of the code that handles Internet Key Exchange version 1 (IKEv1) security negotiation requests.
- 8.8Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability
The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE contains a vulnerability that could allow an authenticated, remote attacker to remotely execute code on an affected system or cause an...
- 9.8Cisco IOS and IOS XE Remote Code Execution Vulnerability
A vulnerability in the Cisco Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a reload of an affected device or...
- 7.5Cisco IOS Software Common Industrial Protocol Request Denial-of-Service Vulnerability
There is a vulnerability in the implementation of the Common Industrial Protocol (CIP) feature in Cisco IOS could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial...
- 7.5Cisco IOS Software for Cisco Industrial Ethernet Switches PROFINET Denial-of-Service Vulnerability
A vulnerability in the implementation of the PROFINET Discovery and Configuration Protocol (PN-DCP) for Cisco IOS could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a...
Which IOS flaws are most likely to be used?
Ranked by the latest exploit-likelihood forecast: the chance each flaw is used in an attack in the next 30 days. A high severity score on its own doesn't tell you that. Flaws shared by many other makers' products are left out.
- >99%
A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service...
- 99%
A vulnerability in the Cisco Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a reload of an affected device or...
- 96%CVE-1999-0016Medium
Land IP denial of service.
- 88%
The server IKEv1 implementation in Cisco IOS 12.2 through 12.4 and 15.0 through 15.6, IOS XE through 3.18S, IOS XR 4.3.x and 5.0.x through 5.2.x, and PIX before 7.0 allows remote attackers to obtain sensitive...
- 80%CVE-2002-1359Critical
Multiple SSH2 servers and clients do not properly handle large packets or large fields, which may allow remote attackers to cause a denial of service or possibly execute arbitrary code via buffer overflow attacks, as...
- 70%
The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE Software contains multiple vulnerabilities that could allow an authenticated, remote attacker to remotely execute code on an affected...
- 68%CVE-2001-0537Critical
HTTP server for Cisco IOS 11.3 to 12.2 allows attackers to bypass authentication and execute arbitrary commands, when local authorization is being used, by specifying a high access level in the URL.
- 45%
A vulnerability in the SNMP implementation of could allow an authenticated, remote attacker to cause a reload of the affected system or to remotely execute code.
Running IOS? We'll keep checking.
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1 flaw being exploited affects software Acme tracks
Cisco IOS 12.4 contains multiple cross-site forgery vulnerabilities that allows remote attackers to execute arbitrary commands via (1) a certain "show privilege" command to the /level/15/exec/- URI, and (2) a certain "alias exec" command to the /level/15/exec/-/configure/http URI.
- Matched to
- IOS on Acme's software list
- What to do
- Patch first, then check for signs of use
Sent to the alert recipients Acme chose. Also in the app and to Acme's webhook.
We track 598 published vulnerabilities listed under the name IOS, across 8,443 versions. The most recent IOS flaw added to the known-exploited list is CVE-2008-4128, on 13 July 2026.
38 are on the list of flaws known to be exploited. The most recently added are CVE-2008-4128, CVE-2023-20109 and CVE-2004-1464.
Cisco also lists IOS under more specific names, such as IOS XE and IOS XR. Flaws listed only under those names are counted on their own pages, not here. Open the release you run to see its own list.
Each flaw names its own versions, usually as ranges. The newest, CVE-2008-4128, affects 12.4. The versions for every exploited flaw are listed on this page.
Create a Precursor Intelligence account and track IOS. We match it against every published flaw, give each one a risk score from 0 to 100 and keep watching, so you hear about new ones as soon as we know, by email, in the app or by webhook.