CVE-2026-47071· NVD / CVE Program· CNA EEF

SOCKS5 TLS upgrade ignores caller timeout in hackney

Noroxi assessment

Priority: Monitor (action score 32/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.70% (FIRST EPSS); higher than 52.6% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: benoitc hackney 4.0.1, 5ccdab725c561a6f03d05a51f2d0664f98236dae.

Low priority for now. Upgrade to benoitc hackney 4.0.1, 5ccdab725c561a6f03d05a51f2d0664f98236dae or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Uncontrolled Resource Consumption vulnerability in benoitc hackney allows Flooding. The SOCKS5 transport in src/hackney_socks5.erl correctly applies the caller-supplied timeout to the SOCKS5 negotiation phase, but then upgrades the connection to TLS using the two-argument form ssl:connect/2, which defaults to an infinite timeout. The Timeout value is in scope at the call site but is not forwarded. A hostile SOCKS5 proxy that completes the SOCKS5 handshake normally and then goes silent (or sends a partial TLS ServerHello and stalls) will cause the connecting process to block indefinitely, regardless of the connect_timeout or recv_timeout options supplied by the caller. This issue affects hackney: from 0.10.0 before 4.0.1.

HighCVSS 8.2 · v4.0—No exploit Fix available

Published: May 25, 2026
Updated: Jul 24, 2026
EPSS: 0.7% · 52th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 32 / 40 · 8.2 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.7%

CISA SSVC decision

Exploitation: proof of concept
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · EEF: 8.2; NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
benoitc	hackney	cpe:2.3:a:benoitc:hackney

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

benoitc hackney0.10.0 and later · before 4.0.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

benoitc hackney
- 0.10.0 and later · before 4.0.1affected · semver
- 34cdbd1d20a282aacc286a89327465a3925b4c5d and later · before 5ccdab725c561a6f03d05a51f2d0664f98236daeaffected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Hex	hackney	from 0.10.0 · before 4.0.1	4.0.1

Same product

benoitc: all records

Other highest-scoring records for the same primary product.

CVE-2026-47073Unbounded memory consumption in WebSocket client in hackney
34Monitor
CVE-2026-47067Atom table exhaustion via unrecognized URL schemes in hackney
34Monitor
CVE-2026-47066Infinite loop in Alt-Svc header parser in hackney
34Monitor

Published before and after this one in the same product

← EarlierCVE-2026-47069May 25, 2026 · CRLF injection in cookie domain/path options in hackney
8Monitor
← EarlierCVE-2026-47070May 25, 2026 · HTTP/3 redirect handler leaks Authorization and Cookie headers to cross-origin redirect target in hackney
24Monitor
Later →CVE-2026-47072May 25, 2026 · CRLF injection in WebSocket upgrade request in hackney
27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
benoitc hackney	4.0.1	Vendor (CNA)
benoitc hackney	5ccdab725c561a6f03d05a51f2d0664f98236dae	Vendor (CNA)
Hex:hackney	4.0.1	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

benoitc/hackneycommit 5ccdab7

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Peter Ullrichfinder
Benoit Chesneauremediation developer
Jonatan Männchen / EEFanalyst

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-470730 days apartUnbounded memory consumption in WebSocket client in hackney
34Monitor
CVE-2026-470770 days apartUnbounded body accumulation in HTTP/3 response loop in hackney
32Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:07 PM UTC

For records you follow, these changes also arrive as notifications. →

References

cna.erlef.org/cves/CVE-2026-47071.html

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records