CVE-2026-8468

Unbounded buffer accumulation in multipart header parsing causes denial of service in plug

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Published May 14, 2026 CVSS 4.0 · 8.2 High EPSS < 1% KEV · Not listed
Description
Allocation of Resources Without Limits or Throttling vulnerability in plug_project plug allows denial of service via unbounded buffer accumulation in multipart header parsing.

'Elixir.Plug.Conn':read_part_headers/2 in lib/plug/conn.ex does not obey its :length parameter. There is no upper bound on the size of the accumulated buffer. By contrast, the sibling function read_part_body has an explicit byte_size(acc) > length guard that stops accumulation once a limit is reached. No such guard exists in read_part_headers. An unauthenticated remote attacker can exhaust server memory by sending a crafted multipart/form-data request, causing a denial of service.

This issue affects plug from 1.4.0 before 1.15.4, 1.16.3, 1.17.1, 1.18.2, and 1.19.2.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-468c-vq7p-gh64 Plug: Unbounded buffer accumulation in multipart header parsing causes denial of service
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}
Type Values Removed Values Added
First Time appeared Elixir-plug
Elixir-plug plug Cowboy
Vendors & Products Elixir-plug
Elixir-plug plug Cowboy
Type Values Removed Values Added
Description Allocation of Resources Without Limits or Throttling vulnerability in plug_project plug allows denial of service via unbounded buffer accumulation in multipart header parsing. plug_multipart in src/plug_multipart.erl is a fork of the cow_multipart module from ninenines cowboy (CVE-2026-8466). The same unbounded accumulation pattern is present in 'Elixir.Plug.Conn':read_part_headers/2 in lib/plug/conn.ex: it accumulates incoming request bytes into a growing binary with no upper-bound check. When plug_multipart:parse_headers/2 returns more or {more, Buffer}, the function reads up to 64 KB from the underlying socket and recurses with the enlarged buffer. There is no equivalent of the byte_size(acc) > length guard present in the sibling function read_part_body/8. An unauthenticated attacker can send a multipart/form-data request whose body never yields a complete header section — for example, a body that never contains the advertised boundary delimiter, or one whose header lines never contain \r\n\r\n — and force the server process to accumulate memory linearly with the bytes the protocol layer is willing to deliver. A handful of concurrent such uploads is sufficient to exhaust BEAM memory. This issue affects plug from 1.4.0 before 1.15.4, 1.16.3, 1.17.1, 1.18.2, and 1.19.2. Allocation of Resources Without Limits or Throttling vulnerability in plug_project plug allows denial of service via unbounded buffer accumulation in multipart header parsing. 'Elixir.Plug.Conn':read_part_headers/2 in lib/plug/conn.ex does not obey its :length parameter. There is no upper bound on the size of the accumulated buffer. By contrast, the sibling function read_part_body has an explicit byte_size(acc) > length guard that stops accumulation once a limit is reached. No such guard exists in read_part_headers. An unauthenticated remote attacker can exhaust server memory by sending a crafted multipart/form-data request, causing a denial of service. This issue affects plug from 1.4.0 before 1.15.4, 1.16.3, 1.17.1, 1.18.2, and 1.19.2.
Type Values Removed Values Added
Description Allocation of Resources Without Limits or Throttling vulnerability in plug_project plug allows denial of service via unbounded buffer accumulation in multipart header parsing. plug_multipart in src/plug_multipart.erl is a fork of the cow_multipart module from ninenines cowboy (CVE-2026-8466). The same unbounded accumulation pattern is present in 'Elixir.Plug.Conn':read_part_headers/2 in lib/plug/conn.ex: it accumulates incoming request bytes into a growing binary with no upper-bound check. When plug_multipart:parse_headers/2 returns more or {more, Buffer}, the function reads up to 64 KB from the underlying socket and recurses with the enlarged buffer. There is no equivalent of the byte_size(acc) > length guard present in the sibling function read_part_body/8. An unauthenticated attacker can send a multipart/form-data request whose body never yields a complete header section — for example, a body that never contains the advertised boundary delimiter, or one whose header lines never contain \r\n\r\n — and force the server process to accumulate memory linearly with the bytes the protocol layer is willing to deliver. A handful of concurrent such uploads is sufficient to exhaust BEAM memory. This issue affects plug from 1.4.0 before 1.15.4, 1.16.3, 1.17.1, 1.18.2, and 1.19.2.
Title Unbounded buffer accumulation in multipart header parsing causes denial of service in plug
First Time appeared Plug Project
Plug Project plug
Weaknesses CWE-770
CPEs cpe:2.3:a:plug_project:plug:*:*:*:*:*:*:*:*
Vendors & Products Plug Project
Plug Project plug
References
Metrics cvssV4_0

{'score': 8.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}
Weaknesses

Sources

Status
PUBLISHED
Assigner
EEF
Published
Updated
May 27, 2026, 3:41 PM
Reserved
May 13, 2026, 11:44 AM

View source JSON

Updated
May 14, 2026, 5:54 PM

JSON

Status
Deferred
Published
May 14, 2026, 11:16 AM
Modified
Oct 26, 2026, 2:10 PM

View source JSON

No data.

Updated
May 14, 2026, 2:32 PM

JSON