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CVE-2026-55163 medium CVSS 6.3

Authorization Flaw in lemur (CVE-2026-55163)

Summary

Vulnerability in lemur (CVE-2026-55163). Risk of unauthorized operations or information disclosure. Exploitable via PUT /api/1/roles/. Mitigation: upgrade to 1.9.2 or later.

Original description

The description as published by the source.

Summary

The PUT /api/1/roles/ handler in lemur/roles/views.py gates only on RoleMemberPermission(role_id).can(), which is satisfied for any user who is already a member of the target role. The handler then passes data["users"] and data["name"] directly to service.update(), permitting any role member to rewrite that role's membership list and name. The companion DELETE handler on the same resource is correctly gated by @admin_permission.require; the asymmetry between PUT and DELETE on identical resources indicates an authorization oversight rather than a deliberate design choice.

Root Cause

lemur/roles/views.py:298:

permission = RoleMemberPermission(role_id)
if permission.can():
    return service.update(
        role_id, data["name"], data.get("description"), data.get("users")
    )
return dict(message="You are not authorized to modify this role."), 403
 
@admin_permission.require(http_exception=403)
def delete(self, role_id):
    ...

lemur/auth/permissions.py:56:

class RoleMemberPermission(Permission):
    def __init__(self, role_id):
        needs = [RoleNeed("admin"), RoleMemberNeed(role_id)]
        super().__init__(*needs)

flask_principal.Permission.allows() is OR-semantic across needs, so RoleMemberPermission(role_id).can() returns True if the caller is either an admin or a member of role_id. The PUT handler treats membership-of-self as sufficient to mutate the role; DELETE does not.

Af…

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-2026-55163 has been found in lemur.
Attackers can target a specific entry point like PUT /api/1/roles/ over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.3/10.
What to do: upgrade lemur to 1.9.2 or later.
If unsure, ask your IT team or search "lemur CVE-2026-55163" on the vendor's site.

CVE-2026-55163 (lemur) — CWE-863 / CVSS v3 6.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: PUT /api/1/roles/ / DELETE / True / role_id
Patched: 1.9.2 — 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

Incorrect authorization (CWE-863) exists in lemur. Attackers reach the vulnerable code path via PUT /api/1/roles/.

📍 Affected scope

Check the vendor advisory for the affected versions of lemur. Attack surface: PUT /api/1/roles/ / DELETE / True / role_id.

🔥 Severity

Severity: Medium (CVSS 6.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.9.2.

🛡️ 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 PUT /api/1/roles/ requests with malformed payloads or SQL meta-characters. Run grep -r 'lemur' . 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

  1. 1
    Identify exposure identify 
    grep -r 'lemur' . | 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 lemur を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'PUT /api/1/roles/' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで PUT /api/1/roles/ への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade lemur to 1.9.2

    ステージング環境で 1.9.2 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 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against PUT /api/1/roles/ on staging to confirm patch closes the vector

    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 2 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

pip lemur
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.2"}]}]
PyPI lemur
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.2"}]}]

References

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