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Unbounded HTTP/1 response-header and chunked-trailer accumulation allows memory-exhaustion DoS

High
whatyouhide published GHSA-qrfr-wh4c-3qhw Jul 14, 2026

Package

erlang mint (Erlang)

Affected versions

>= 0.1.0 and < 1.9.2

Patched versions

1.9.2

Description

Summary

Mint's HTTP/1 response parser accumulates every parsed response header (and every chunked-trailer header) into an unbounded per-request list that only clears when the terminating blank line arrives. A remote HTTP server reachable by the Mint client (directly, via SSRF, via an attacker-controlled redirect target, or via a man-in-the-middle) can stream complete header or trailer lines forever, growing connection state on the client until the BEAM node is killed by the operating system's out-of-memory handler.

Details

1. Unbounded response-header accumulator. Mint.HTTP1.decode_headers/5 in lib/mint/http1.ex walks the response header section by calling the underlying line parser and prepending each {name, value} tuple to a growing list. When the incoming TCP segment ends mid-section, the accumulated list is stashed in request.headers_buffer and the trailing bytes in conn.buffer, ready to resume on the next Mint.HTTP1.stream/2 invocation. The section is only released when the parser returns :eof (the terminating blank line), and nothing in between caps the number of headers or the byte size of the section.

2. Same pattern for chunked trailers. Mint.HTTP1.decode_trailer_headers/4 reuses the same accumulator-plus-headers_buffer shape for HTTP/1.1 chunked trailers. After a zero-size chunk, the parser enters trailer mode and every trailer line is prepended to a list stored on the request across stream/2 calls, again only terminated by :eof.

3. Underlying parser has no built-in cap. Mint.HTTP1.Response.decode_header/1 in lib/mint/http1/response.ex invokes :erlang.decode_packet(:httph_bin, binary, []) with an empty option list, so the packet_size and line_length options both default to 0 (unlimited). No layer between the socket and the accumulator constrains the section.

4. Denial of service. A malicious server sends the status line (or, for the trailer variant, Transfer-Encoding: chunked plus a small chunk followed by 0\r\n) and then streams complete header or trailer lines indefinitely without ever writing the closing blank line. The client's conn state grows on every stream/2 call, driving the BEAM process resident set until the OS OOM-kills the node.

PoC

  1. Point a Mint HTTP/1 client at an attacker-controlled origin (direct connection, SSRF, or a redirect the client auto-follows).
  2. From that origin, respond with HTTP/1.1 200 OK\r\n followed by a stream of minimal header lines (A:\r\n, or larger X-Pad-N: <junk>\r\n for faster growth) and never emit the closing \r\n.
  3. The client's normal Mint.HTTP1.stream/2 receive loop grows request.headers_buffer and conn.buffer on every packet until the BEAM node is OOM-killed. The chunked-trailer variant substitutes Transfer-Encoding: chunked, a single small chunk, 0\r\n, and then an endless stream of trailer lines.

Impact

Any application using Mint as an HTTP/1 client is vulnerable whenever it can be induced to talk to an attacker-controlled server, whether directly, through an auto-followed redirect, through SSRF, or through a network man-in-the-middle. A single such connection is enough to exhaust the BEAM node's memory and terminate the entire application process.

References

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
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

CVE ID

CVE-2026-58229

Weaknesses

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. Learn more on MITRE.

Credits