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CVE-2026-42554
medium
CVSS 6.1
Cross-Site Scripting (XSS) in github.com/gofiber/fiber/v3 (CVE-2026-42554)
Summary
cross-site scripting in github.com/gofiber/fiber/v3 (CVE-2026-42554). Risk of unauthorized operations or information disclosure. Exploitable via ``DefaultRes.AutoFormat``. Mitigation: upgrade to `3.2.0` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-42554** has been found in github.com/gofiber/fiber/v3.
Attackers can target a specific entry point like ``DefaultRes.AutoFormat`` over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.1/10.
What to do: upgrade github.com/gofiber/fiber/v3 to **3.2.0** or later.
If unsure, ask your IT team or search "github.com/gofiber/fiber/v3 CVE-2026-42554" on the vendor's site.
CVE-2026-42554 (github.com/gofiber/fiber/v3) — CWE-79 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: `DefaultRes.AutoFormat` / `Ctx.Format` / `JSON` / `XML`
Patched: `3.2.0` — 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.
❓ What is the problem
**Cross-site scripting (XSS)** (CWE-79) exists in github.com/gofiber/fiber/v3. Attackers reach the vulnerable code path via ``DefaultRes.AutoFormat`` without authentication.
📍 Affected scope
github.com/gofiber/fiber/v3 — . Attack surface: `DefaultRes.AutoFormat` / `Ctx.Format` / `JSON` / `XML`.
🔥 Severity
Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **3.2.0**.
🛡️ Workaround
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
🔍 Detection
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run `grep -r 'github.com/gofiber/fiber/v3' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'github.com/gofiber/fiber/v3' . | 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 `github.com/gofiber/fiber/v3` を grep し、稼働しているサービス・バージョンを把握する。
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6Apply patch patch
Upgrade github.com/gofiber/fiber/v3 to 3.2.0ステージング環境で 3.2.0 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と、Step 3 で見つけた異常検知の続報チェックを含めること。
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7Post-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 Step 3 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
go
github.com/gofiber/fiber/v3
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.2.0"}]}]
go
github.com/gofiber/fiber/v2
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.52.13"}]}]