hono: Permissive Cross-domain Security Policy with Untrusted Domains
CVE-2026-54290 is a high-severity permissive cross-domain security policy with untrusted domains vulnerability in hono from Honojs, 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. Affected hono versions: < 4.12.25. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.33% 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
- Check which version of hono you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.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
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
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N. Scored by CNA (github.com).
Official description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.25, with credentials: true and no explicit origin (the default wildcard), the CORS Middleware reflects the request's Origin and sends Access-Control-Allow-Credentials: true. Any site can then make credentialed cross-origin requests and read the responses, exposing cookie-authenticated endpoints to arbitrary origins. This vulnerability is fixed in 4.12.25.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Permissive Cross-domain Security Policy with Untrusted Domains
The product uses a web-client protection mechanism such as a Content Security Policy (CSP) or cross-domain policy file, but the policy includes untrusted domains with which the web client is allowed to communicate.
How developers prevent this class of flaw
- Define a restrictive Content Security Policy or cross-domain policy file.
- Avoid using wildcards in the CSP / cross-domain policy file. Any domain matching the wildcard expression will be implicitly trusted, and can perform two-way interaction with the target server.
- For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.
More Permissive Cross-domain Security Policy with Untrusted Domains vulnerabilities (CWE-942)
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
Other vulnerabilities in hono
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
Recent Permissive Cross-domain Security Policy with Untrusted Domains vulnerabilities
- 8.1 High severity
- 7.5 High severity
- 9.4 Critical severity
- 8.1 High severity
- 8.1 High severity
- 9.6 Critical severity
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