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CVE-2026-48818 high CVSS 7.5

SSRF (Server-Side Request Forgery) in starlette (CVE-2026-48818)

Summary

SSRF in starlette (CVE-2026-48818). Confidential information can be exposed externally. Exploitable via StaticFiles. Mitigation: upgrade to 1.1.0 or later.

Original description

The description as published by the source.

Summary

When serving static files on Windows, StaticFiles resolves the requested path with os.path.realpath. If a UNC path (such as \\attacker.com\share) reaches the resolver, realpath causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-controlled host, which can then be cracked offline or relayed to other hosts.

Details

StaticFiles.lookup_path() joins the requested path onto the served directory and calls os.path.realpath on the result before checking containment with os.path.commonpath. On Windows, a UNC path is absolute, so os.path.join discards the served directory and realpath resolves the bare UNC path, triggering the outbound SMB connection and NTLM authentication before the containment check rejects the path. The HTTP response is a benign 404, but the credential disclosure has already happened. POSIX systems are not affected.

This only affects the default configuration (follow_symlink=False), which uses os.path.realpath. The follow_symlink=True branch uses [`os.path.a…

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-2026-48818 has been found in starlette.
Attackers can target a specific entry point like StaticFiles over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade starlette to 1.1.0 or later.
If unsure, ask your IT team or search "starlette CVE-2026-48818" on the vendor's site.

CVE-2026-48818 (starlette) — CWE-918 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: StaticFiles / os.path.realpath / realpath / os.path.commonpath
Patched: 1.1.0 — 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

SSRF (CWE-918) exists in starlette. Attackers reach the vulnerable code path via StaticFiles without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of starlette. Attack surface: StaticFiles / os.path.realpath / realpath / os.path.commonpath.

🔥 Severity

Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 1.1.0.

🛡️ 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 'starlette' . 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 'starlette' . | 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 starlette 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
    Apply patch patch 
    Upgrade starlette to 1.1.0

    ステージング環境で 1.1.0 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を含めること。

  3. 3
    Post-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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip starlette
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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