CVE-2026-71850 — Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure
Hono is a Web application framework that provides support for any JavaScript runtime. From 3.8.0 to 4.12.33, memo() from hono/jsx retains the result of a server side render and reuses it for later renders with comparator equal props, and request scoped values read inside the component take no part in that comparison, so a response can contain HTML rendered for another user's request. Components wrapped with memo() are compared by props alone; values read implicitly during rendering, such as JSX Context through createContext() and useContext(), useRequestContext() from hono/jsx-renderer, and getContext() from hono/context-storage, do not participate, and the retained result lives as long as the wrapped component, so it outlives the request that produced it. A user may receive a response containing HTML rendered for another user when both render the same memoized component with comparator equal props on the same warm instance, which may disclose another user's account or profile data, disclose request scoped secrets embedded in HTML such as CSRF tokens, or expose role specific content to users who should not receive it. This issue is fixed in version 4.12.34.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (medium)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Honojs Hono).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 4.8 | CVSS 3.1 | Medium | 1.2 | 3.6 | security-advisories@github.com via NIST National Vulnerability Database |
| 4.8 | CVSS 3.1 | Medium | — | — | GitHub_M via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N (score shown at the top: security-advisories@github.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · honojs/hono
- SSVC assessment updated
- Record published
- CVSS changed · 4.8
- Source status changed · → Deferred
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
1 on the record
Elsewhere on this site
Related CVEs (same products)
- Medium CVE-2026-109955 Hono 4.12.4 before 4.13.11 Middleware Bypass via serveStatic Double Decoding 2d
- Medium CVE-2026-69207 Hono: ReDoS in CORS middleware via Access-Control-Request-Headers Aug 7, 2026
- Low CVE-2026-71849 Hono: Proxy Helper does not remove response headers listed in the `Connection` header Aug 7, 2026
- Medium CVE-2026-71848 Hono: Algorithmic Complexity DoS in Language Middleware Aug 7, 2026
- Medium CVE-2026-59895 Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility Jul 8, 2026
- Medium CVE-2026-59897 Hono: API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication Jul 8, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-71850 is "Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure", rated Medium. It affects Hono (Honojs); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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