# CVE-2026-115701: Cowboy HTTP/1.1 Unbounded Buffering of Pipelined Data During Request Handling Enables Memory Exhaustion

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

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 onward.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/ninenines/cowboy/commit/3a630c07e1521abf63a1b9ea080509aa1337b60d

## Affected products and versions

- ninenines / cowboy (cowboy): ≥ 2.18.0; < * (affected, semver). Source: CNA: EEF
- ninenines / cowboy (ninenines/cowboy): ≥ faf5594fbf74530ace90b0c46c936bdc2cf82081; < 3a630c07e1521abf63a1b9ea080509aa1337b60d (affected, git). Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 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; source: CNA: EEF

- CVSS 4.0: 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/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; source: NVD: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://cna.erlef.org/cves/CVE-2026-115701.html (CNA: EEF; related, third-party-advisory)

- https://osv.dev/vulnerability/EEF-CVE-2026-115701 (CNA: EEF; related)

- https://github.com/ninenines/cowboy/commit/faf5594fbf74530ace90b0c46c936bdc2cf82081 (CNA: EEF; related)

- https://github.com/ninenines/cowboy/commit/3a630c07e1521abf63a1b9ea080509aa1337b60d (CNA: EEF; patch)

- https://cna.erlef.org/cves/CVE-2026-115701.html (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/ninenines/cowboy/commit/3a630c07e1521abf63a1b9ea080509aa1337b60d (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://github.com/ninenines/cowboy/commit/faf5594fbf74530ace90b0c46c936bdc2cf82081 (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

- https://osv.dev/vulnerability/EEF-CVE-2026-115701 (6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-115701; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-115701; retrieved 2026-11-06; source updated 2026-11-06

Revision: 02f620d95a9fc01d01411a6022d65ab60b8be3a0554533176b40eb3923421bdf

Canonical: https://y2.dev/cve/CVE-2026-115701

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