CVE-2026-53537
Description
A flaw was found in Python-Multipart. This vulnerability allows a remote attacker to bypass security controls by exploiting a difference in how Content-Disposition and Content-Type headers are parsed. Specifically, the parse_options_header function incorrectly applies RFC 2231/5987 decoding, which is forbidden for multipart/form-data. This discrepancy enables an attacker to smuggle a malicious field name or filename past upstream security devices, potentially leading to information disclosure on the backend system.
Statement
This Low impact information disclosure flaw in python-multipart stems from a parsing discrepancy in Content-Disposition and Content-Type headers. When deployed with upstream components like WAFs or proxies that do not implement RFC 2231/5987 decoding for multipart/form-data, an attacker could smuggle different field names or filenames. This allows bypassing security controls, but requires a specific network configuration for exploitation, increasing attack complexity.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | 5.3 | 3.7 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | Low | Low | Low |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Red Hat CVSS v3 Score Explanation
RH agreed with GitHub's AC:H since the CVSS spec defines AC:H as "conditions beyond the attacker's control must exist" and the presence of a non-RFC-2231-aware upstream validator is exactly that.
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
Frequently Asked Questions
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