Quick answers
- Is CVE-2026-47066 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-47066 being exploited in the wild.
- How severe is CVE-2026-47066?
- High severity, with a CVSS score of 8.7, published 25 May 2026.
- Which products and versions are affected?
- Benoit Chesneau Hackney >= 2.0.0-beta.1, < 4.0.1, >= 2.0.0, < 4.0.1.
- Is there a fix for CVE-2026-47066?
- A patch was published on 2026-06-26: Fixed in version 4.0.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-47066 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-47066?
- Check whether you run Benoit Chesneau Hackney at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an infinite loop (CWE-835) located in `src/hackney_altsvc.erl`. When the `Alt-Svc` header parser encounters a non-token byte (such as `!`, `@`, or `=`) at the start of an entry, the `parse_token/2` function fails to consume any input and returns the original buffer. Because `parse_entries/2` does not detect this lack of progress, it recursively calls itself with the identical buffer, resulting in a tight tail-recursive loop. This pins an Erlang scheduler at 100% CPU and prevents the process from yielding. The issue is reachable via any synchronous HTTP response containing the malicious header and is fixed in version 4.0.1.
Affected products
- benoitc hackney >= 2.0.0, < 4.0.1
Identifiers
- CVE-2026-47066
- GHSA-6cp8-v795-jr2j
Timeline
- 2026-05-25: disclosed: NVD publication date
- 2026-06-26: advisory: GitHub Advisory published
- 2026-06-26: patched: Fixed in version 4.0.1