Authorization Flaw in lemur (CVE-2026-48508)
Summary
Vulnerability in lemur (CVE-2026-48508). Successful exploitation can lead to full system takeover. Exploitable via POST /api/1/authorities. Mitigation: upgrade to 1.9.1 or later.
Original description
The description as published by the source.
Summary
StrictRolePermission and AuthorityCreatorPermission in lemur/auth/permissions.py call flask_principal.Permission.__init__() with zero Needs when their config flags are unset. Both flags defaulted to False in code prior to the fix, so this was the state of any Lemur install that hadn't explicitly opted in.
Flask-Principal's Permission.allows() returns True whenever self.needs is empty. The .can() gate therefore passes for every authenticated identity, including the lowest-privilege role Lemur ships (read-only).
A user holding only read-only can create root Certificate Authorities, create and edit notifications (an SSRF sink), create domain entries, and upload arbitrary certificates. These classes are the sole authorization check on those endpoints.
Root Cause
# lemur/auth/permissions.py
class AuthorityCreatorPermission(Permission):
def __init__(self):
requires_admin = current_app.config.get("ADMIN_ONLY_AUTHORITY_CREATION", False)
if requires_admin:
super().__init__(RoleNeed("admin"))
else:
super().__init__() # empty Need set
class StrictRolePermission(Permission):
def __init__(self):
strict_role_enforcement = current_app.config.get("LEMUR_STRICT_ROLE_ENFORCEMENT", False)
if strict_role_enforcement:
needs = [RoleNeed("admin"), RoleNeed("operator")]
super().__init__(*needs)
else:
super().__init__()…
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-2026-48508 has been found in lemur.
Attackers can target a specific entry point like POST /api/1/authorities over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: upgrade lemur to 1.9.1 or later.
If unsure, ask your IT team or search "lemur CVE-2026-48508" on the vendor's site.
CVE-2026-48508 (lemur) — CWE-863 / CVSS v3 8.8
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /api/1/authorities / PUT /api/1/authorities/ / StrictRolePermission / AuthorityCreatorPermission
Patched: 1.9.1 — 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.
Incorrect authorization (CWE-863) exists in lemur. Attackers reach the vulnerable code path via POST /api/1/authorities.
Check the vendor advisory for the affected versions of lemur. Attack surface: POST /api/1/authorities / PUT /api/1/authorities/ / StrictRolePermission / AuthorityCreatorPermission.
Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.
Update to 1.9.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /api/1/authorities 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
-
1Identify 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。 -
2Hunt for indicators of compromise detect
grep 'POST /api/1/authorities' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /api/1/authorities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。 -
3Apply patch patch
Upgrade lemur to 1.9.1ステージング環境で 1.9.1 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。
-
4Post-deployment verification verify
Replay attack against POST /api/1/authorities 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
References
- package github.com
- web github.com
- web github.com
- web security-advisories@github.com
- web security-advisories@github.com