CVE-2011-5331: Distributed Ruby (aka DRuby) 1.8 mishandles instance_eval.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2011-5331 is a critical-severity flaw (CVSS 9.8) affecting distributed ruby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Distributed Ruby (aka DRuby) 1.8 mishandles instance_eval.

Why this priority

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

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Published	2019-11-18
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: distributed ruby project

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-11-18 18:15 UTCPublished CVE record published
2026-06-16 23:36 UTCUpdated Record last modified

distributed ruby project distributed ruby DOWNGRADE

Affected: 1.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.8

1. Check installed version

apt-cache policy distributed-ruby || rpm -q distributed-ruby || distributed-ruby --version

2. No fixed release: DOWNGRADE to a release before 1.8 (Debian / Ubuntu)

apt-cache madison distributed-ruby sudo apt install distributed-ruby=<VERSION_BEFORE_1.8> sudo apt-mark hold distributed-ruby

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list distributed-ruby sudo dnf downgrade distributed-ruby-<VERSION_BEFORE_1.8> sudo dnf versionlock add distributed-ruby

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-2011-5331?

distributed ruby: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2011-5331 being exploited?

CVE-2011-5331 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-2011-5331 affect?

CVE-2011-5331 affects distributed ruby. Severity is critical (CVSS 9.8). Distributed Ruby (aka DRuby) 1.8 mishandles instance_eval.

How urgent is CVE-2011-5331?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

Related CVEs

CVE-2011-5330 CRITICAL 9.8 DOWNGRADE Distributed Ruby (aka DRuby) 1.8 mishandles the sending of syscalls.

References

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