CVE-2026-20281 Denial of service in Cisco Session Initiation Protocol (SIP) Software
Remote attackers can cause denial of service on Cisco IP phones by sending crafted HTTP packets, requiring Web Access to be enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20281?
CVE-2026-20281 is a high-severity denial of service vulnerability in Cisco Session Initiation Protocol (SIP) Software, published on 2 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-401
Which versions are affected by CVE-2026-20281?
How do I fix CVE-2026-20281?
No fix has been published for CVE-2026-20281 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-20281 being exploited?
There is no known exploitation of CVE-2026-20281 in the wild and no public exploit code.
Sources
Also known as GHSA-998p-wvfv-584p.