Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the HTTP Server feature of Cisco IOS Software and Cisco IOS XE Software Release 3E could allow an authenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition.
This vulnerability is due to improper validation of user-supplied input. An attacker could exploit this vulnerability by sending malformed HTTP requests to an affected device. A successful exploit could allow the attacker to cause a watchdog timer to expire and the device to reload, resulting in a DoS condition. To exploit this vulnerability, the attacker must have a valid user account.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-http-dos-sbv8XRpLThis advisory is part of the March 2026 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: March 2026 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
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Vulnerable Products
This vulnerability affects Cisco devices if they are running a vulnerable release of Cisco IOS Software or IOS XE Software Release 3E and they have the HTTP Server feature enabled with an active WEB_EXEC module.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the HTTP Server Configuration
To determine whether a device that is running a vulnerable software release is using a vulnerable configuration, use the following steps.
Step 1. Determine Whether the HTTP Server Is Enabled
To determine whether the HTTP Server feature is enabled on a device, log in to the device and use the show running-config | include ip http server|secure command in the CLI to check for the presence of the ip http server command or the ip http secure-server command in the global configuration. If either command is present, the HTTP Server feature is enabled for the device.
The following example shows the output of the show running-config | include ip http server|secure command for a device that has the HTTP Server feature enabled:
Router# show running-config | include ip http server|secure|active
ip http server
ip http secure-serverNote: The presence of either command or both commands in the device configuration indicates that the web UI feature is enabled.
If the command returns output, proceed to Step 2. If the output is empty, the device is not affected by this vulnerability.
Step 2. Determine Whether WEB_EXEC Module Is Active
To determine whether a device uses the WEB_EXEC module, use the show ip http server session-module | include Status|WEB_EXEC command in the CLI.
If the output in Step 1 included ip http server, check the value of Status in the command output. If Status is Active, the device is affected by this vulnerability over HTTP.
If the output in Step 1 included ip http secure-server, check the value of Secure-status in the command output. If Secure-status is Active, the device is affected by this vulnerability over HTTPS.
The following example shows the output of the show ip http server session-module | include Status|WEB_EXEC command. This device is not affected by this vulnerability because Status and Secure-status for WEB_EXEC are both Inactive.
Router#show ip http server session-module | include Status|WEB_EXEC
Session module Name Handle Status Secure-status Description
WEB_EXEC 5 Inactive Inactive HTTP based IOS EXEC ServerThe following example shows the outputs of the commands in both steps. This device is not affected by this vulnerability because only the HTTPS server is enabled and Secure-status for WEB_EXEC is Inactive.
Router# show running-config | include ip http server|secure
ip http secure-server
Router#show ip http server session-module | include Status|WEB_EXEC
Session module Name Handle Status Secure-status Description
WEB_EXEC 5 Active Inactive HTTP based IOS EXEC ServerProducts Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following Cisco products:
- IOS XE 16 and IOS XE 17 Software
- IOS XR Software
- NX-OS Software
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There are no workarounds that address this vulnerability.
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Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To fully remediate this vulnerability and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”).
To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to determine whether a release is affected by any Cisco Security Advisory. To use the form, follow these steps:
- Choose which advisories the tool will search—only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
- Enter a release number—for example, 15.9(3)M2 or 17.3.3.
- Click Check.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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This vulnerability was found during internal security testing by T.VE of the Cisco Advanced Security Initiatives Group (ASIG).
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2026-MAR-25
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SOFTWARE DOWNLOADS AND TECHNICAL SUPPORT
The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool. Please note that customers may download only software that was procured from Cisco directly or through a Cisco authorized reseller or partner and for which the license is still valid.
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC). Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
When considering software upgrades, customers are advised to regularly consult the advisories for the relevant Cisco products to determine exposure and a complete upgrade solution. In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
LEGAL DISCLAIMER DETAILS
CISCO DOES NOT MAKE ANY EXPRESS OR IMPLIED GUARANTEES OR WARRANTIES OF ANY KIND, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. WITHOUT LIMITING THE GENERALITY OF THE FOREGOING, CISCO DOES NOT GUARANTEE THE ACCURACY OR COMPLETENESS OF THIS INFORMATION. THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
Copies or summaries of the information contained in this Security Advisory may lack important information or contain factual errors. Customers are advised to visit the Cisco Security Advisories page for the most recent version of this Security Advisory. The Cisco Product Security Incident Response Team (PSIRT) assesses only the affected and fixed release information that is documented in this advisory. See the Cisco Security Vulnerability Policy for more information.