CVE-2018-3759: private_address_check ruby gem before 0.5.0 is vulnerable to a time-of-check time-of-use (TOCTOU) race conditi

Q: How do I fix CVE-2018-3759?

private address check: upgrade to 0.5.0. Exact commands for each OS are on this page.

Q: Is CVE-2018-3759 being exploited?

CVE-2018-3759 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2018-3759 affect?

CVE-2018-3759 affects private address check. Severity is low (CVSS 3.7). private_address_check ruby gem before 0.5.0 is vulnerable to a time-of-check time-of-use (TOCTOU) race condition due to the address the socket uses not being checked. DNS entries with a TTL of 0 can trigger this case where the initial resol

Q: How urgent is CVE-2018-3759?

Priority 31/100. Remotely exploitable, no login, no user action

Routine

LOW 3.7REMOTEUPGRADE

CVE-2018-3759 is a low-severity flaw (CVSS 3.7) affecting private address check. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

private_address_check ruby gem before 0.5.0 is vulnerable to a time-of-check time-of-use (TOCTOU) race condition due to the address the socket uses not being checked. DNS entries with a TTL of 0 can trigger this case where the initial resolution is a public address but the subsequent resolution is a private address.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-362
Published	2018-06-13
Last modified	2026-06-17

Publisher (CNA): HackerOne · Vendor: private address check project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-06-13 15:29 UTCPublished CVE record published
2026-06-17 01:57 UTCUpdated Record last modified

private address check project private address check UPGRADE

Affected: < 0.5.0

Fixed in: 0.5.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy private-address-check || rpm -q private-address-check || private-address-check --version

2. UPGRADE to 0.5.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade private-address-check

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade private-address-check

Note

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

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-2018-3759?

private address check: upgrade to 0.5.0. Exact commands for each OS are on this page.

Is CVE-2018-3759 being exploited?

CVE-2018-3759 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-2018-3759 affect?

CVE-2018-3759 affects private address check. Severity is low (CVSS 3.7). private_address_check ruby gem before 0.5.0 is vulnerable to a time-of-check time-of-use (TOCTOU) race condition due to the address the socket uses not being checked. DNS entries with a TTL of 0 can trigger this case where the initial resol

How urgent is CVE-2018-3759?

Priority 31/100. Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

Related CVEs

CVE-2017-0909 CRITICAL 9.8 UPGRADE The private_address_check ruby gem before 0.4.1 is vulnerable to a bypass due to an incomplete blacklist of co
CVE-2017-0904 HIGH 8.1 UPGRADE The private_address_check ruby gem before 0.4.0 is vulnerable to a bypass due to use of Ruby's Resolv.getaddre

References

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