How severe is CVE-2026-47072?

No CVSS score has been assigned to CVE-2026-47072 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-47072?

CVE-2026-47072 affects the following packages: hackney (Hex). Ecosystems affected: Hex.

How do I fix CVE-2026-47072?

Update hackney to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47072 is resolved across your whole dependency graph.

How do I detect CVE-2026-47072 in my Hex dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hackney, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-47072 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-47072 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-47072 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-47072?

CVE-2026-47072 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 43th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-47072?

CVE-2026-47072 is classified as CWE-93 (CWE-93). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-47072 published, and has it been updated?

CVE-2026-47072 was published on May 25, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💧 Hex

Not in CISA KEV

CVE-2026-47072 — hackney

Fix: benoitc/hackney@52310ca

CVE-2026-47072 is a CWE-93 vulnerability in hackney. A fix is available for hackney — see the affected versions and patch details below.

CRLF injection in WebSocket upgrade request in hackney

Also known asEEF-CVE-2026-47072GHSA-f9vr-g2g2-x9fg

Published

May 25, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-47072.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

💧hackney

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Hex packages — download data is not available via public APIs for these ecosystems.

Description

Summary

CRLF injection in hackney's WebSocket upgrade request builder (src/hackney_ws.erl). init/1 copies the host, path, headers, and protocols options from the caller-supplied opts map verbatim into #ws_data{}, and do_handshake/1 splices them directly into the raw HTTP/1.1 upgrade request by binary concatenation with no \r\n or \0 stripping. A caller that passes any of these fields from untrusted input can inject arbitrary header lines into the outbound upgrade request.

Details

do_handshake/1 builds the upgrade request at several concatenation sites:

Host header (lines 583–590): the host binary is written straight into Host: <host>:<port>\r\n.
Sec-WebSocket-Protocol (lines 601–602): protocol tokens are joined with , and appended as a header line.
Extra headers (line 606): caller-supplied {Name, Value} tuples are concatenated as Name: Value\r\n with no sanitization of either component.
Request path (line 611): the path is interpolated into the GET <path> HTTP/1.1\r\n request line.

None of these sites reject \r, \n, or \0. A header value like <<"benign\r\nAuthorization: Bearer token">> produces two distinct header lines on the wire. A path with an embedded \r\n rewrites the request line itself.

PoC

Call :hackney_ws.start_link/1 with headers: [{"X-User", "v\r\nAuthorization: Bearer attacker"}].
Connect to a raw TCP listener and capture the bytes hackney writes.
The request contains a standalone Authorization: Bearer attacker line that the upstream WebSocket server parses as a legitimate header.

Impact

Header injection / request smuggling in outbound WebSocket upgrades. Affects hackney 2.0.0 through 4.0.0 wherever host, path, headers, or protocols options are populated from network or user input. Consequences include forging authentication headers toward the upstream server, log and cache poisoning, and request smuggling through intermediary proxies. CVSS v4.0: 6.9 (MEDIUM).

Resources

Introduction commit: https://github.com/benoitc/hackney/commit/690cecaf236fba49526da404a5bc889a24367a3e
Patch commit: https://github.com/benoitc/hackney/commit/52310ca807e7b48441ba0e9129171f535313fdd1

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💧Hex	`hackney`	≥ 2.0.0&&< 4.0.1	4.0.1`mix deps.update hackney`

Affected Products

1 product · 1 configurations

Application

hackneybenoitc

≥ 2.0.0 && < 4.0.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hackney, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hackney to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47072 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary CRLF injection in hackney's WebSocket upgrade request builder (`src/hackney_ws.erl`). `init/1` copies the `host`, `path`, `headers`, and `protocols` options from the caller-supplied opts map verbatim into `#ws_data{}`, and `do_handshake/1` splices them directly into the raw HTTP/1.1 upgrade request by binary concatenation with no `\r\n` or `\0` stripping. A caller that passes any of these fields from untrusted input can inject arbitrary header lines into the outbound upgrade request. ### Details `do_handshake/1` builds the upgrade request at several concatenation sites: - **Hos

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