Cisco Identity Services Engine Software: Deserialization of Untrusted Data
CVE-2025-20124 is a high-severity deserialization of untrusted data vulnerability in Cisco Identity Services Engine Software from Cisco, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected Cisco Identity Services Engine Software versions: 3.0.0; 3.0.0 p1; 3.0.0 p2, 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 18.5% chance of exploitation within 30 days, which is in the top 2.71% of all scored CVEs.
EPSS places it among the vulnerabilities most likely to be exploited soon.
What to do
- Update Identity Services Engine to 3.1 or a later version.
- 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 | Cisco Identity Services Engine Software | 3.0.0; 3.0.0 p1; 3.0.0 p2; 3.0.0 p3; 3.1.0; 3.0.0 p4; 3.1.0 p1; 3.0.0 p5; and 23 more ranges | Not stated |
| Cisco | Cisco ISE Passive Identity Connector | 3.0.0; 3.2.0; 3.1.0; 3.3.0 | Not stated |
| Cisco | Identity Services Engine | before 3.1; 3.1.0; 3.2.0; 3.3.0 | 3.1 |
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
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.9 | Critical | CNA (cisco.com) |
| CVSS 3.1 | 7.2 | High | NVD |
Official description
A vulnerability in an API of Cisco ISE could allow an authenticated, remote attacker to execute arbitrary commands as the root user on an affected device. This vulnerability is due to insecure deserialization of user-supplied Java byte streams by the affected software. An attacker could exploit this vulnerability by sending a crafted serialized Java object to an affected API. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges. Note: To successfully exploit this vulnerability, the attacker must have valid read-only administrative credentials. In a single-node deployment, new devices will not be able to authenticate during the reload time.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
How developers prevent this class of flaw
- If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
- Explicitly define a final object() to prevent deserialization.
More Deserialization of Untrusted Data vulnerabilities (CWE-502)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in Cisco Identity Services Engine Software
- 10.0 Critical severity
- 7.6 High severity
- 7.2 High severity
- 8.6 High severity
- 7.1 High severity
- 9.1 Critical severity
Recent Deserialization of Untrusted Data vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
- 7.2 High severity
- 8.8 High severity
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