Cross-user data disclosure via persistent SSR memoization
Published Aug 7, 2026 · Updated Aug 7, 2026
Exposure of data to the wrong session in Hono 3.8.0 through 4.12.33 allows remote authenticated users to receive another user's SSR output. memo() in hono/jsx caches a component's rendered result by props alone and reuses it after the request-scoped context that produced it has ended. Exploitation requires server-side rendering, a memoized component that reads ambient request state, comparator-equal props, and both requests on the same warm instance; disclosed output can include profile data or embedded CSRF tokens.
Summary
What happened
Exposure of data to the wrong session in Hono 3.8.0 through 4.12.33 allows remote authenticated users to receive another user's SSR output. memo() in hono/jsx caches a component's rendered result by props alone and reuses it after the request-scoped context that produced it has ended. Exploitation requires server-side rendering, a memoized component that reads ambient request state, comparator-equal props, and both requests on the same warm instance; disclosed output can include profile data or embedded CSRF tokens.
The record
- CVE
- CVE-2026-71850
- Published
- Aug 7, 2026
- Updated
- Aug 7, 2026
- Vendor
- Hono
- Product
- Hono
- Classifications
- CWE-488
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 7, 2026CVE publishedPublication date reported by the CVE source.
- Aug 7, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 3.8.0, < 4.12.34
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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