← Back
CVE-2026-55761
medium
CVSS 5.9
Authentication Bypass in github.com/portainer/portainer (CVE-2026-55761)
Summary
authentication bypass in github.com/portainer/portainer (CVE-2026-55761). Data can be tampered with by attackers. Exploitable via ``bouncer.PublicAccess``. Mitigation: upgrade to `2.43.0` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-55761** has been found in github.com/portainer/portainer.
Attackers can target a specific entry point like ``bouncer.PublicAccess`` over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 5.9/10.
What to do: upgrade github.com/portainer/portainer to **2.43.0** or later.
If unsure, ask your IT team or search "github.com/portainer/portainer CVE-2026-55761" on the vendor's site.
CVE-2026-55761 (github.com/portainer/portainer) — CWE-287 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: `bouncer.PublicAccess` / `develop`
Patched: `2.43.0` — 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
**authentication bypass** (CWE-287) exists in github.com/portainer/portainer. Attackers reach the vulnerable code path via ``bouncer.PublicAccess`` without authentication.
📍 Affected scope
github.com/portainer/portainer — . Attack surface: `bouncer.PublicAccess` / `develop`.
🔥 Severity
Severity: Medium (CVSS 5.9/10). Data can be tampered with by attackers
🔧 How to fix
Update to **2.43.0**.
🛡️ 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/portainer/portainer' .` 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/portainer/portainer' . | 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/portainer/portainer` を grep し、稼働しているサービス・バージョンを把握する。
-
6Apply patch patch
Upgrade github.com/portainer/portainer to 2.43.0ステージング環境で 2.43.0 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。
-
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/portainer/portainer
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.43.0"}]}]
References
- web https://github.com/portainer/portainer/commit/49f19107cf9a3540cbe406c9eb7f24390e1af02b
- web https://github.com/portainer/portainer/commit/d2b56efcb4e43c4168bb6688eee9f6bf22867312
- web https://github.com/portainer/portainer/issues/2770
- web https://github.com/portainer/portainer/releases/tag/2.39.4
- web https://github.com/portainer/portainer/releases/tag/2.43.0
- web https://github.com/portainer/portainer/security/advisories/GHSA-x626-fcwx-f5pc
- web https://nvd.nist.gov/vuln/detail/CVE-2026-55761
- web https://github.com/advisories/GHSA-x626-fcwx-f5pc