Cisco Session Initiation Protocol (SIP) Software: Stack-based Buffer Overflow
CVE-2025-20350 is a high-severity stack-based buffer overflow vulnerability in Cisco Session Initiation Protocol (SIP) Software from Cisco, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Session Initiation Protocol (SIP) Software versions: 12.1(1)SR1; 11.5(1); 10.3(2), and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update IP Phone 8865 Firmware to 14.3\(1\) or a later version.
- Update IP Phone 7811 Firmware to 14.3\(1\) or a later version.
- Update IP Phone 7821 Firmware to 14.3\(1\) or a later version.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Session Initiation Protocol (SIP) Software | 12.1(1)SR1; 11.5(1); 10.3(2); 10.2(2); 10.3(1); 10.3(1)SR4; 11.0(1); 10.4(1)SR2 3rd Party; and 32 more ranges | Not stated |
| Cisco | Desk Phone 9871 Firmware | 3.0\(1\) through 3.2\(1\) | Not stated |
| Cisco | Desk Phone 9841 Firmware | 3.0\(1\) through 3.2\(1\) | Not stated |
| Cisco | Desk Phone 9851 Firmware | 3.0\(1\) through 3.2\(1\) | Not stated |
| Cisco | Desk Phone 9861 Firmware | 3.0\(1\) through 3.2\(1\) | Not stated |
| Cisco | IP Phone 8865 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 7811 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 7821 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 7841 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 7861 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8811 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8832 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8841 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8845 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8851 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | IP Phone 8861 Firmware | before 14.3\(1\); 14.3\(1\) | 14.3\(1\) |
| Cisco | Video Phone 8875 Firmware | before 2.3\(1\); 3.0\(1\) through 3.2\(1\); 2.3\(1\) | 2.3\(1\) |
| Cisco | IP Phone 8821 Firmware | before 11.0\(1\); 11.0\(0.7\); 11.0\(1\); 11.0\(2\); 11.0\(3\); 11.0\(4\); 11.0\(5\); 11.0\(6\) | 11.0\(1\) |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the web UI of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 running Cisco SIP Software could allow an unauthenticated, remote attacker to cause a DoS condition on an affected device. This vulnerability is due to a buffer overflow when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending crafted HTTP input to the device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. Note: To exploit this vulnerability, the phone must be registered to Cisco Unified Communications Manager and have Web Access enabled. Web Access is disabled by default.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Stack-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the stack.
How developers prevent this class of flaw
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Implement and perform bounds checking on input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Cisco Session Initiation Protocol (SIP) Software
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
Recent Stack-based Buffer Overflow vulnerabilities
- 9.8 Critical severity
F5 BIG-IP Stack-Based Buffer Overflow Exploited
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
Spotted an error? Tell us.