IOS: Uncaught Exception
CVE-2025-20171 is a high-severity uncaught exception vulnerability in IOS from Cisco, with a CVSS 3.1 base score of 7.7 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected IOS versions: 12.2(33)CX; 12.2(33)CY; 12.2(33)CY1, 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 0.78% chance of exploitation within 30 days, higher than 56% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of IOS you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | IOS | 12.2(33)CX; 12.2(33)CY; 12.2(33)CY1; 12.2(33)CY2; 12.2(58)SE; 12.2(58)SE1; 12.2(58)SE2; 12.2(58)EX; and 32 more ranges | Not stated |
| Cisco | Cisco IOS XE Software | 3.2.0SG; 3.2.1SG; 3.2.2SG; 3.2.3SG; 3.2.4SG; 3.2.5SG; 3.2.6SG; 3.2.7SG; and 32 more ranges | Not stated |
| Cisco | iOS Xe | 3.2.0se; 3.2.0sg; 3.2.1se; 3.2.1sg; 3.2.2se; 3.2.2sg; 3.2.3se; 3.2.3sg; and 32 more ranges | Not stated |
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
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- 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:L/UI:N/S:C/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the SNMP subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to cause a DoS condition on an affected device. This vulnerability is due to improper error handling when parsing SNMP requests. An attacker could exploit this vulnerability by sending a crafted SNMP request to an affected device. A successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition. This vulnerability affects SNMP versions 1, 2c, and 3. To exploit this vulnerability through SNMP v2c or earlier, the attacker must know a valid read-write or read-only SNMP community string for the affected system. To exploit this vulnerability through SNMP v3, the attacker must have valid SNMP user credentials for the affected system.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Uncaught Exception
An exception is thrown from a function, but it is not caught.
How developers prevent this class of flaw
- The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem.
- A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added.
- Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in IOS
- 8.6 High severity
- 7.7 High severity
- 8.6 High severity
- 9.0 Critical severity
- 7.7 High severity
- 7.7 High severity
Recent Uncaught Exception vulnerabilities
- 7.7 High severity
- 7.7 High severity
- 7.7 High severity
- 8.7 High severity
- 7.5 High severity
- 7.5 High severity
Spotted an error? Tell us.