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CVE-2026-55164 medium CVSS 4.9

Vulnerability in lemur (CVE-2026-55164)

Summary

Vulnerability in lemur (CVE-2026-55164). Confidential information can be exposed externally. Exploitable via PUT /api/1/users/. Mitigation: upgrade to 1.9.2 or later.

Original description

The description as published by the source.

Summary

lemur.users.service.update() writes a user's new password as plaintext to the users.password column. The User model wires bcrypt hashing to SQLAlchemy's before_insert event but registers no equivalent listener for before_update, and service.update() does not call user.hash_password() after assigning the new value. Every password change performed through the admin-gated PUT /api/1/users/ endpoint persists the user's password to the database in cleartext.

Root Cause

lemur/users/models.py:

# line 38
class User(BaseModel):
    __tablename__ = "users"
    id = Column(Integer, primary_key=True)
    password = Column(String(128))            # plain column, no setter, no Vault descriptor

# line 74
    def hash_password(self):
        if self.password:
            self.password = bcrypt.generate_password_hash(self.password).decode("utf-8")

# line 111
listen(User, "before_insert", hash_password)  # only before_insert is wired

lemur/users/service.py:

# line 46
def update(user_id, username, email, active, profile_picture, roles, password=None):
    ...
    user = get(user_id)
    user.username = username
    user.email = email
    user.active = active
    user.profile_picture = profile_picture
    if password:
        user.password = password              # raw assignment
    update_roles(user, roles)
    return database.update(user)              # commits, no hashing

No before_update listener exists. `User.password…

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-2026-55164 has been found in lemur.
Attackers can target a specific entry point like PUT /api/1/users/ over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 4.9/10.
What to do: upgrade lemur to 1.9.2 or later.
If unsure, ask your IT team or search "lemur CVE-2026-55164" on the vendor's site.

CVE-2026-55164 (lemur) — CWE-256 / CVSS v3 4.9
Attack vector: remote (network-reachable) / no user interaction
Attack surface: PUT /api/1/users/ / users.password / User / before_insert
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

A vulnerability (CWE-256) exists in lemur. Attackers reach the vulnerable code path via PUT /api/1/users/.

📍 Affected scope

Check the vendor advisory for the affected versions of lemur. Attack surface: PUT /api/1/users/ / users.password / User / before_insert.

🔥 Severity

Severity: Medium (CVSS 4.9/10). Confidential information can be exposed externally.

🔧 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/users/ 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/users/' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで PUT /api/1/users/ 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/users/ 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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