Cisco Session Initiation Protocol Software up to 14.4(1)SR2 denial of service

Summaryinfo

A vulnerability marked as critical has been reported in Cisco Session Initiation Protocol Software. This affects an unknown function. Performing a manipulation results in denial of service. This vulnerability is identified as CVE-2026-20281. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as critical has been found in Cisco Session Initiation Protocol Software. This affects an unknown code. The manipulation with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. The summary by CVE is:

A vulnerability in Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 that are running Cisco Session Initiation Protocol (SIP) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted HTTP packets to the device. A successful exploit could allow the attacker to cause the affected device to continuously consume memory, resulting in a DoS condition. A manual reboot of the device is required to recover from this condition. Note: For this vulnerability to be exploitable, the phone must be registered to Cisco Unified Communications Manager (Unified CM) and have Web Access enabled. Web Access is disabled by default.

The advisory is shared at sec.cloudapps.cisco.com. This vulnerability is uniquely identified as CVE-2026-20281 since 10/08/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/02/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Cisco

Name

• Session Initiation Protocol Software

Version

• 2.0(1)
• 2.1(1)
• 2.2(1)
• 2.3(1)
• 2.3(1)SR1
• 3.0(1)
• 3.1(1)
• 3.1(1)SR1
• 3.2(1)
• 3.3(1)
• 3.4(1)
• 3.5(1)
• 3.5(1)SR1
• 3.6(1)
• 4.0(1)
• 4.1(1)
• 4.1(1)SR1
• 9.3(3)
• 10.1(1)SR1
• 10.1(1)SR2
• 10.1(1.9)
• 10.2(1)
• 10.2(1)SR1
• 10.2(2)
• 10.3(1)
• 10.3(1)SR1
• 10.3(1)SR2
• 10.3(1)SR3
• 10.3(1)SR4
• 10.3(1)SR4b
• 10.3(1)SR5
• 10.3(1)SR6
• 10.3(1)SR7
• 10.3(2)
• 11-0-1MSR1-1
• 11.0(0.7) MPP
• 11.0(1)
• 11.0(2)
• 11.0(2)SR1
• 11.0(2)SR2
• 11.0(3)
• 11.0(3)SR1
• 11.0(3)SR2
• 11.0(3)SR3
• 11.0(3)SR4
• 11.0(3)SR5
• 11.0(3)SR6
• 11.0(4)
• 11.0(4)SR1
• 11.0(4)SR2
• 11.0(4)SR3
• 11.0(5)
• 11.0(5)SR1
• 11.0(5)SR2
• 11.0(5)SR3
• 11.0(6)
• 11.0(6)SR1
• 11.0(6)SR2
• 11.0(6)SR4
• 11.0(6)SR5
• 11.0(6)SR6
• 11.0(6)SR7
• 11.5(1)
• 11.5(1)SR1
• 11.7(1)
• 12.0(1)
• 12.0(1)SR1
• 12.0(1)SR2
• 12.0(1)SR3
• 12.1(1)
• 12.1(1)SR1
• 12.5(1)
• 12.5(1)SR1
• 12.5(1)SR2
• 12.5(1)SR3
• 12.6(1)
• 12.6(1)SR1
• 12.7(1)
• 12.7(1)SR1
• 12.8(1)
• 12.8(1)SR1
• 12.8(1)SR2
• 14.0(1)
• 14.0(1)SR1
• 14.0(1)SR2
• 14.0(1)SR3
• 14.1(1)
• 14.1(1)SR1
• 14.1(1)SR2
• 14.1(1)SR3
• 14.2(1)
• 14.2(1)SR1
• 14.2(1)SR2
• 14.2(1)SR3
• 14.2(1)SR4
• 14.3(1)
• 14.3(1)SR1
• 14.3(1)SR2
• 14.3(1)SR3
• 14.4(1)
• 14.4(1)SR1
• 14.4(1)SR2

License

• commercial

Website

• Vendor: https://www.cisco.com/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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