CVE-2026-47066: Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Alloc

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-47066 is a high-severity flaw (CVSS 7.5) affecting hackney. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receives a non-token, non-whitespace, non-comma byte (e.g. !, @, =, ;), it returns the input unchanged. skip_comma/1 also returns the buffer unchanged when the first byte is not a comma. parse_entries/2 then recurses

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 45%)
CISA exploited list	No
Weakness	CWE-835
Published	2026-05-25
Last modified	2026-07-24

Publisher (CNA): EEF · Vendor: benoitc

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-25 15:16 UTCPublished CVE record published
2026-07-24 10:10 UTCUpdated Record last modified

benoitc hackney UPGRADE

Affected: >= 2.0.0 and < 4.0.1

Fixed in: 4.0.1

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy hackney || rpm -q hackney || hackney --version

2. UPGRADE to 4.0.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade hackney

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hackney

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison hackney sudo apt install hackney=<VERSION_BEFORE_2.0.0> sudo apt-mark hold hackney

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list hackney sudo dnf downgrade hackney-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add hackney

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-47066?

hackney: upgrade to 4.0.1. Exact commands for each OS are on this page.

Is CVE-2026-47066 being exploited?

CVE-2026-47066 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-47066 affect?

CVE-2026-47066 affects hackney. Severity is high (CVSS 7.5). Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receiv

How urgent is CVE-2026-47066?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-47075 HIGH 7.5 UPGRADE Improper Neutralization of CRLF Sequences vulnerability in benoitc hackney allows HTTP Request Splitting
CVE-2026-47073 HIGH 7.5 UPGRADE Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding
CVE-2026-47067 HIGH 7.5 UPGRADE Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding
CVE-2026-47071 HIGH 7.5 UPGRADE Uncontrolled Resource Consumption vulnerability in benoitc hackney allows Flooding
CVE-2026-47077 HIGH 7.5 UPGRADE Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding

References

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