CVE-2026-47076: hackney SSRF — Exploit & Fix

Description

Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP's uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller's allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney's normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost. This issue affects hackney: from 0.13.0 before 4.0.1.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0016

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-436 CWE-436

CWE-918 Server-Side Request Forgery (SSRF)

Affected Products

Vendor	Product	Versions
benoitc	hackney	0.13.0 — 4.0.1

References

Advisories & Patches

https://cna.erlef.org/cves/CVE-2026-47076.html https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq https://osv.dev/vulnerability/EEF-CVE-2026-47076 https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq

Exploits

https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq

Frequently Asked Questions

What is CVE-2026-47076? +

Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP's uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller's allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney's normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost. This issue affects hackney: from 0.13.0 before 4.0.1. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-47076? +

CVE-2026-47076 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0016, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-47076? +

CVE-2026-47076 affects products from benoitc, specifically: hackney. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-47076? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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