CVE-2026-29045
Hono ≤ 4.12.4
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NSummary
CVE-2026-29045 is a high-severity Hex Encoding (CWE-177) vulnerability in Hono Hono. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 36th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-29045 affects Hono, a web application framework supporting any JavaScript runtime, in versions prior to 4.12.4. The vulnerability arises from inconsistent URL decoding when using the serveStatic middleware alongside route-based protections, such as app.use('/admin/*', ...). Specifically, Hono's router employs decodeURI, while serveStatic uses decodeURIComponent, creating a mismatch that permits paths with encoded slashes (%2F) to bypass middleware checks yet resolve to the intended filesystem location. This issue, classified under CWE-177 (Incorrect Handling of URL Encoding), carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high confidentiality impact.
Remote, unauthenticated attackers can exploit this vulnerability over the network with low complexity and no user interaction. By crafting requests with %2F-encoded paths targeting protected static resources, attackers bypass route middleware authorizations, gaining unauthorized read access to sensitive files served via serveStatic without triggering protective logic.
The issue has been addressed in Hono version 4.12.4, as detailed in the project's security advisory (GHSA-q5qw-h33p-qvwr) and the patching commit (6a0607a929d888893f0c91d92dce2fcfdb3662a3). Security practitioners should upgrade to 4.12.4 or later and review applications using serveStatic with path-based middleware for exposure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9506
Vulnerability Data
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, when using serveStatic together with route-based middleware protections (e.g. app.use('/admin/*', ...)), inconsistent URL decoding allowed protected static resources to be accessed without authorization.…
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The router used decodeURI, while serveStatic used decodeURIComponent. This mismatch allowed paths containing encoded slashes (%2F) to bypass middleware protections while still resolving to the intended filesystem path. This issue has been patched in version 4.12.4.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.2.2
Mitigating Controls (NIST 800-53 r5) AI
Proper input validation requires decoding and checking URL-encoded data before use, directly stopping the weakness from being exploitable.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require correct URL-encoding/decoding and input validation during development.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development catches URL-decoding flaws before release, but does not itself define coding rules.
Secure SDLC processes include validation steps that reduce CWE-177, yet the control is broader than this single weakness.
Application security requirements explicitly call for input validation and canonicalization, directly preventing improper URL decoding.
Secure coding standards mandate proper handling and decoding of encoded inputs, eliminating CWE-177.