data/reports/GO-2023-1705.yaml

id: GO-2023-1705
modules:
    - module: std
      versions:
        - fixed: 1.19.8
        - introduced: 1.20.0-0
        - fixed: 1.20.3
      vulnerable_at: 1.20.2
      packages:
        - package: mime/multipart
          symbols:
            - Reader.readForm
            - mimeHeaderSize
            - newPart
            - Part.populateHeaders
            - Reader.NextPart
            - Reader.NextRawPart
            - Reader.nextPart
            - readMIMEHeader
          derived_symbols:
            - Reader.ReadForm
        - package: net/textproto
          symbols:
            - readMIMEHeader
          derived_symbols:
            - Reader.ReadMIMEHeader
summary: Excessive resource consumption in net/http, net/textproto and mime/multipart
description: |-
    Multipart form parsing can consume large amounts of CPU and memory when
    processing form inputs containing very large numbers of parts.

    This stems from several causes:

    1. mime/multipart.Reader.ReadForm limits the total memory a parsed multipart
    form can consume. ReadForm can undercount the amount of memory consumed, leading
    it to accept larger inputs than intended.
    2. Limiting total memory does not account for increased pressure on the garbage
    collector from large numbers of small allocations in forms with many parts.
    3. ReadForm can allocate a large number of short-lived buffers, further
    increasing pressure on the garbage collector.

    The combination of these factors can permit an attacker to cause an program that
    parses multipart forms to consume large amounts of CPU and memory, potentially
    resulting in a denial of service. This affects programs that use
    mime/multipart.Reader.ReadForm, as well as form parsing in the net/http package
    with the Request methods FormFile, FormValue, ParseMultipartForm, and
    PostFormValue.

    With fix, ReadForm now does a better job of estimating the memory consumption of
    parsed forms, and performs many fewer short-lived allocations.

    In addition, the fixed mime/multipart.Reader imposes the following limits on the
    size of parsed forms:

    1. Forms parsed with ReadForm may contain no more than 1000 parts. This limit
    may be adjusted with the environment variable GODEBUG=multipartmaxparts=.
    2. Form parts parsed with NextPart and NextRawPart may contain no more than
    10,000 header fields. In addition, forms parsed with ReadForm may contain no
    more than 10,000 header fields across all parts. This limit may be adjusted with
    the environment variable GODEBUG=multipartmaxheaders=.
credits:
    - Jakob Ackermann (@das7pad)
references:
    - report: https://go.dev/issue/59153
    - fix: https://go.dev/cl/482076
    - fix: https://go.dev/cl/482075
    - fix: https://go.dev/cl/482077
    - web: https://groups.google.com/g/golang-announce/c/Xdv6JL9ENs8
cve_metadata:
    id: CVE-2023-24536
    cwe: 'CWE-400: Uncontrolled Resource Consumption'
    references:
        - https://security.netapp.com/advisory/ntap-20230526-0007/
        - https://security.gentoo.org/glsa/202311-09
review_status: REVIEWED