Vulnerability-Lookup

CVE-2026-28356 (GCVE-0-2026-28356)

Vulnerability from cvelistv5 – Published: 2026-03-12 16:45 – Updated: 2026-03-13 16:29

Title

ReDoS in multipart 1.3.0 - `parse_options_header()`

Summary

multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

GitHub_M

References

URL

Tags

https://github.com/defnull/multipart/security/adv…

x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	defnull	multipart	Affected: >= 1.3.0, < 1.3.1 Affected: < 1.2.2

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-28356

Vulnerability from fkie_nvd - Published: 2026-03-12 17:16 - Updated: 2026-03-12 21:07

Severity ?

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/defnull/multipart/security/advisories/GHSA-p2m9-wcp5-6qw3

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev."
    },
    {
      "lang": "es",
      "value": "multipart es un r\u00e1pido analizador de multipart/form-data para Python. Antes de 1.2.2, 1.3.1 y 1.4.0-dev, la funci\u00f3n parse_options_header() en multipart.py utiliza una expresi\u00f3n regular con una alternancia ambigua, lo que puede causar retroceso exponencial (ReDoS) al analizar encabezados HTTP o de segmento multipart maliciosamente elaborados. Esto puede ser abusado para ataques de denegaci\u00f3n de servicio (DoS) contra aplicaciones web que utilizan esta biblioteca para analizar encabezados de solicitud o flujos de multipart/form-data. El problema est\u00e1 solucionado en 1.2.2, 1.3.1 y 1.4.0-dev."
    }
  ],
  "id": "CVE-2026-28356",
  "lastModified": "2026-03-12T21:07:53.427",
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      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
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GHSA-P2M9-WCP5-6QW3

Vulnerability from github – Published: 2026-03-12 18:32 – Updated: 2026-03-12 18:32

Summary

multipart vulnerable to ReDoS in `parse_options_header()`

Details

Summary

The parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams.

Impact

Any WSGI or ASGI application using multipart.parse_form_data() directly or indirectly (e.g. while parsing multipart/form-data streams) is vulnerable. The slow-down is significant enough to block request handling threads for multiple seconds per request.

Affected versions

All versions up to and including 1.3.0 are affected. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "multipart"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.3.0"
            },
            {
              "fixed": "1.3.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "multipart"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.2.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-28356"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-12T18:32:18Z",
    "nvd_published_at": "2026-03-12T17:16:50Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe `parse_options_header()` function in `multipart.py` uses a regular expression with an *ambiguous alternation*, which can cause *exponential backtracking (ReDoS)* when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for **denial of service (DoS)** attacks against web applications using this library to parse request headers or `multipart/form-data` streams.\n\n## Impact\n\nAny WSGI or ASGI application using `multipart.parse_form_data()` directly or indirectly (e.g. while parsing `multipart/form-data` streams) is vulnerable. The slow-down is significant enough to block request handling threads for multiple seconds per request.\n\n## Affected versions\n\nAll versions up to and including `1.3.0` are affected. The issue is fixed in `1.2.2`, `1.3.1` and `1.4.0-dev`.",
  "id": "GHSA-p2m9-wcp5-6qw3",
  "modified": "2026-03-12T18:32:18Z",
  "published": "2026-03-12T18:32:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/defnull/multipart/security/advisories/GHSA-p2m9-wcp5-6qw3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-28356"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/defnull/multipart"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "multipart vulnerable to ReDoS in `parse_options_header()`"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-28356 (GCVE-0-2026-28356)

FKIE_CVE-2026-28356

GHSA-P2M9-WCP5-6QW3

Summary

Impact

Affected versions

Tags

Sightings

Nomenclature