Authentication Bypass in arduino-esp32 (CVE-2026-42855)
Summary
Authentication bypass in arduino-esp32 (CVE-2026-42855). Confidential information can be exposed externally. Exploitable via Authorization header. Mitigation: upgrade to 3.3.8 or later.
Original description
The description as published by the source.
arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2 microcontrollers. Prior to 3.3.8, the WebServer Digest authentication implementation in arduino-esp32 computes the authentication hash using the URI field from the client's Authorization header, without verifying that it matches the actual requested URI. This allows an attacker who possesses any valid digest response (computed for URI-A) to authenticate requests to a completely different protected URI (URI-B), bypassing per-resource access control. This vulnerability is fixed in 3.3.8.
Source: NIST National Vulnerability Database 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-2026-42855 has been found in arduino-esp32.
Attackers can target a specific entry point like Authorization header over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade arduino-esp32 to 3.3.8 or later.
If unsure, ask your IT team or search "arduino-esp32 CVE-2026-42855" on the vendor's site.
CVE-2026-42855 (arduino-esp32) — CWE-287 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Authorization header
Patched: 3.3.8 — 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.
Authentication bypass (CWE-287) exists in arduino-esp32. Attackers reach the vulnerable code path via Authorization header without authentication.
Check the vendor advisory for the affected versions of arduino-esp32. Attack surface: Authorization header.
Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.
Update to 3.3.8.
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 'arduino-esp32' . 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
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1Identify exposure identify
grep -r 'arduino-esp32' . | 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
arduino-esp32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 arduino-esp32 to 3.3.8ステージング環境で 3.3.8 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。
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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。
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov