How severe is CVE-2026-47067?

No CVSS score has been assigned to CVE-2026-47067 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-47067?

CVE-2026-47067 affects the following packages: hackney (Hex). Ecosystems affected: Hex.

How do I fix CVE-2026-47067?

Update hackney to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47067 is resolved across your whole dependency graph.

How do I detect CVE-2026-47067 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-2026-47067 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-47067 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-47067 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-2026-47067?

CVE-2026-47067 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 53th 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-2026-47067?

CVE-2026-47067 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-47067 published, and has it been updated?

CVE-2026-47067 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-2026-47067 — hackney

Fix: benoitc/hackney@31f6f0e

CVE-2026-47067 is a CWE-770 vulnerability in hackney. A fix is available for hackney — see the affected versions and patch details below.

Atom table exhaustion via unrecognized URL schemes in hackney

Also known asEEF-CVE-2026-47067GHSA-9653-rcfr-5c62

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-2026-47067.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs53th percentile — riskier than 53% 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

CVE-2026-47067 is an atom table exhaustion vulnerability (CWE-770) in hackney's URL parser (src/hackney_url.erl). hackney_url:parse_url/1 converts every URL scheme it encounters into a BEAM atom via binary_to_atom/2. Because BEAM atoms are never garbage-collected and the atom table has a hard limit of 1,048,576 entries, an attacker who can feed URLs with attacker-chosen scheme prefixes — directly as request targets, as webhook/callback URLs, or via Location headers in redirect chains — can exhaust the atom table and crash the entire BEAM VM with system_limit.

Details

1. Scheme extraction and conversion

In src/hackney_url.erl, parse_url/1 extracts the scheme binary (the part before ://), validates it with is_valid_scheme/1 (RFC 3986 alphabet: alpha-led, <=19 bytes, alphanumeric/+/-/. body), lowercases it, then calls:

binary_to_atom(SchemeLower, utf8)

The resulting atom is stored on the #hackney_url{} record and returned to the caller.

2. Permanent atom accumulation

The validation constrains the alphabet but not uniqueness. The allowed scheme space is enormous (≈52·65¹⁸ values), far exceeding the default atom limit of 1,048,576. Each distinct scheme mints a new permanent atom. Even when hackney subsequently rejects an unsupported scheme with {error, {unsupported_scheme, _}}, the atom has already been interned and is never reclaimed.

3. Crash vector

The most dangerous path is redirect following: when hackney follows a Location header, the redirect target URL is re-parsed by the same function. An attacker-controlled server can serve a sequence of redirects — or a batch of URLs from an upstream feed — each with a fresh unique scheme, driving the atom count monotonically upward. At the limit the BEAM emits system_limit and the node terminates; recovery requires a full restart.

PoC

Call hackney_url:parse_url/1 (or :hackney.request/5) repeatedly with URLs whose scheme prefixes are unique on each call: aaaa://x, aaab://x, aaac://x, …
After enough iterations, observe erlang:system_info(:atom_count) climbing by one per unique scheme.
At 1,048,576 atoms the VM crashes with system_limit.

Alternatively, point hackney at a server that replies with a feed of ~1M URLs with distinct schemes (or uses redirect chains with rotating schemes); the atom table is exhausted and the node crashes without the client being able to intervene.

Impact

Unauthenticated remote denial of service via permanent resource exhaustion leading to VM termination. Any application using hackney 2.0.0 through 4.0.0 that processes attacker-influenced URLs — direct request targets, webhook URLs, or Location headers in followed redirects — is affected. No authentication or special configuration is required. CVSS v4.0 score: 8.7 (HIGH).

References

Introduction commit: https://github.com/benoitc/hackney/commit/d9713695c0d99855d12c73fd8a0b4be0543950c4
Patch commit: https://github.com/benoitc/hackney/commit/31f6f0e27e096ad88743dfded4f030a3ee74972e

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-2026-47067 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### Summary [CVE-2026-47067](https://nvd.nist.gov/vuln/detail/CVE-2026-47067) is an atom table exhaustion vulnerability (CWE-770) in hackney's URL parser (`src/hackney_url.erl`). `hackney_url:parse_url/1` converts every URL scheme it encounters into a BEAM atom via `binary_to_atom/2`. Because BEAM atoms are never garbage-collected and the atom table has a hard limit of 1,048,576 entries, an attacker who can feed URLs with attacker-chosen scheme prefixes — directly as request targets, as webhook/callback URLs, or via `Location` headers in redirect chains — can exhaust the atom table and crash

O3 Security · Impact-Aware SCA

Is CVE-2026-47067 in your dependencies?

Find it across Hex, including transitive dependencies.

Scan my dependencies How O3 SCA works