Cowboy HTTP/1.1 Unbounded Buffering of Pipelined Data During Request Handling Enables Memory Exhaustion

Summary

CVE	CVE-2026-115701
State	PUBLISHED
Assigner	EEF
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-11-06 11:17:05 UTC
Updated	2026-11-09 16:17:26 UTC
Description	Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP/1.1. Once a request has been received in full and its handler is still running, cowboy_http:parse/2 in src/cowboy_http.erl appends every further byte that arrives on the keep-alive connection to the connection buffer and returns to the receive loop without parsing it. The socket stays in active mode and no limit applies to this buffer: max_request_line_length, max_headers and the other parser limits only take effect once the handler returns and parsing resumes, and the only timer in this state is idle_timeout (default 60 seconds), which is reset on every received chunk. A client can therefore send an arbitrary amount of data on one connection for as long as the handler runs, and a few connections to an endpoint that holds requests open can drive the Erlang VM into out-of-memory conditions. This issue affects cowboy: from 2.18.0 before 2.21.0.

Risk And Classification

Primary CVSS: v4.0 8.2 HIGH from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-770 | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling

Version	Source	Type	Score	Severity	Vector
4.0	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	Secondary	8.2	HIGH	`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/E:X/C...`
4.0	CNA	CVSS	8.2	HIGH	`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`

CVSS v4.0 Breakdown

Attack Vector

Network

Attack Complexity

Low

Attack Requirements

Present

Privileges Required

None

User Interaction

None

Confidentiality

None

Integrity

None

Availability

High

Sub Conf.

None

Sub Integrity

None

Sub Availability

None

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Ninenines	Cowboy	affected 2.18.0 2.21.0 semver	Not specified
CNA	Ninenines	Cowboy	affected faf5594fbf74530ace90b0c46c936bdc2cf82081 3a630c07e1521abf63a1b9ea080509aa1337b60d git	Not specified

References

Reference	Source	Link	Tags
osv.dev/vulnerability/EEF-CVE-2026-115701	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	osv.dev
github.com/ninenines/cowboy/commit/3a630c07e1521abf63a1b9ea080509aa1337b60d	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	github.com
github.com/ninenines/cowboy/commit/faf5594fbf74530ace90b0c46c936bdc2cf82081	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	github.com
cna.erlef.org/cves/CVE-2026-115701.html	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	cna.erlef.org
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Mikica Ivosevic (en)

CNA: Jonatan Männchen / EEF (en)

There are currently no legacy QID mappings associated with this CVE.