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CVE-2026-53537 low CVSS 3.7

Vulnerability in python-multipart (CVE-2026-53537)

Summary

Vulnerability in python-multipart (CVE-2026-53537). Risk of unauthorized operations or information disclosure. Exploitable via parse_options_header. Mitigation: upgrade to 0.0.30 or later.

Original description

The description as published by the source.

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while…

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-2026-53537 has been found in python-multipart.
Attackers can target a specific entry point like parse_options_header over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: upgrade python-multipart to 0.0.30 or later.
If unsure, ask your IT team or search "python-multipart CVE-2026-53537" on the vendor's site.

CVE-2026-53537 (python-multipart) — CWE-20 / CVSS v3 3.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: parse_options_header / email.message.Message / filename / name
Patched: 0.0.30 — 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-20) exists in python-multipart. Attackers reach the vulnerable code path via parse_options_header without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of python-multipart. Attack surface: parse_options_header / email.message.Message / filename / name.

🔥 Severity

Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 0.0.30.

🛡️ 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 'python-multipart' . 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 'python-multipart' . | 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 python-multipart 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 python-multipart to 0.0.30

    ステージング環境で 0.0.30 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 python-multipart
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.0.30"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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