Guardian: URL Redirection to Untrusted Site
CVE-2026-31982 is a high-severity URL redirection to untrusted site vulnerability in Guardian from Nozomi Networks, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 26.2.0 as the first without the flaw, so updating Guardian to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.31% 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 Guardian to 26.2.0 or a later version.
- Update CMC to 26.2.0 or a later version.
- Read the advisory on security.nozominetworks.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.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Nozomi Networks | Guardian | before 26.2.0 | 26.2.0 |
| Nozomi Networks | CMC | before 26.2.0 | 26.2.0 |
| Siemens | RUGGEDCOM APE1808 | all versions | 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
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L. Scored by CNA (nozominetworks.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 5.3 | Medium | CNA (nozominetworks.com) |
| CVSS 3.1 | 7.1 | High | CNA (nozominetworks.com) |
Official description
An Open Redirect vulnerability was discovered in the SAML Single Sign-On functionality due to insufficient validation of a user-controlled redirection parameter. An unauthenticated attacker can craft a request to the SAML sign-in endpoint and poison the cached SAML redirection for other users who subsequently initiate SAML Single Sign-On, enabling phishing and credential-theft attacks, as well as disrupting SAML authentication for all affected users.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: URL Redirection to Untrusted Site
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How developers prevent this class of flaw
- Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
- When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to /login.asp and ID 2 could map to http://www.example.com/. Features such as the ESAPI AccessReferenceMap provide this capability.
- Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application. Be sure that the nonce is not predictable (CWE-330).
More URL Redirection to Untrusted Site vulnerabilities (CWE-601)
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
- security.nozominetworks.com/NN-2026:9-01Mitigation
Other references
Other vulnerabilities in Guardian
- 7.2 High severity
- 7.2 High severity
- 7.5 High severity
- 7.4 High severity
- 8.1 High severity
- 7.5 High severity
Recent URL Redirection to Untrusted Site vulnerabilities
- 7.4 High severity
- 8.8 High severity
- 7.2 High severity
- 8.2 High severity
- 8.0 High severity
- 8.3 High severity
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