Information Disclosure in hono (CVE-2026-71849)
Summary
Vulnerability in hono (CVE-2026-71849). Risk of unauthorized operations or information disclosure. Exploitable via Connection. Mitigation: upgrade to 4.12.34 or later.
Original description
The description as published by the source.
Summary
The Proxy Helper (hono/proxy) does not remove response headers named by the origin's Connection header. Headers that the origin marked as connection-scoped are therefore forwarded to clients.
Details
Per RFC 9110 Section 7.6.1, an intermediary must remove the header fields listed in a message's Connection header field before forwarding the message, in addition to the well-known hop-by-hop headers. The proxy() function removed the well-known hop-by-hop headers (including Connection itself) from origin responses, but did not remove the headers that the response's Connection header field designated as connection-scoped.
This issue arises when an application proxies responses from an origin that declares additional, non-standard headers as hop-by-hop via the Connection response header.
Impact
A client may receive response headers that the origin intended only for its immediate peer. This may lead to:
- Disclosure of connection-scoped or internal metadata contained in such headers
This issue affects applications that use the Proxy Helper (hono/proxy) to forward responses from origins that list custom header names in their Connection response header. Applications whose origins only use the standard hop-by-hop headers are not affected.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-71849 has been found in hono.
Attackers can target a specific entry point like Connection over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: upgrade hono to 4.12.34 or later.
If unsure, ask your IT team or search "hono CVE-2026-71849" on the vendor's site.
CVE-2026-71849 (hono) — CWE-200 / CVSS v3 3.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Connection
Patched: 4.12.34 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Information disclosure (CWE-200) exists in hono. Attackers reach the vulnerable code path via Connection without authentication.
Check the vendor advisory for the affected versions of hono. Attack surface: Connection.
Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.
Update to 4.12.34.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'hono' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'hono' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
honoを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade hono to 4.12.34ステージング環境で 4.12.34 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。