Summaryinfo

A vulnerability, which was classified as critical, was found in Cisco IOS and IOS XE. This vulnerability affects unknown code of the component HTTP Server. Such manipulation leads to improper handling of syntactically invalid structure. This vulnerability is referenced as CVE-2026-20125. It is possible to launch the attack remotely. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Cisco IOS and IOS XE (affected version not known). Affected by this issue is some unknown functionality of the component HTTP Server. The manipulation with an unknown input leads to a improper handling of syntactically invalid structure vulnerability. Using CWE to declare the problem leads to CWE-228. The product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification. Impacted is availability. CVE summarizes:

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.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is handled as CVE-2026-20125 since 10/08/2025. The exploitation is known to be easy. The attack may be launched remotely. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 03/31/2026).

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-15449). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Router Operating System

Vendor

• Cisco

Name

• IOS
• IOS XE

License

• commercial

Website

• Vendor: https://www.cisco.com/

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