GHSA-mqwr-4qf2-2hcv is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in rubygems-update. EPSS puts its 30-day exploitation probability at 15.2% (97th percentile). A fix is available for rubygems-update — see the affected versions and patch details below.
RubyGems vulnerable to Deserialization of Untrusted Data
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-mqwr-4qf2-2hcv plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
rubygems-updateReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
RubyGems versions between 2.0.0 and 2.6.13 are vulnerable to a possible remote code execution vulnerability. YAML deserialization of gem specifications can bypass class white lists. Specially crafted serialized objects can possibly be used to escalate to remote code execution. The issue has been patched in 2.6.14.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rubygems-update | ≥ 2.0.0&&< 2.6.14 | 2.6.14bundle update rubygems-update --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rubygems-update, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rubygems-update to 2.6.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mqwr-4qf2-2hcv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-mqwr-4qf2-2hcv can be triaged on real exposure rather than presence alone.
Tailored to GHSA-mqwr-4qf2-2hcv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This issue did not affect the versions of rubygems as shipped with Red Hat Enterprise Linux 6. This issue affects the versions of ruby as shipped with Red Hat Enterprise Linux 7 and the versions of rh-ruby22-ruby and rh-ruby23-ruby as shipped with Red Hat Software Collections. Red Hat Product Security has rated this…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 7 | ruby-0:2.0.0.648-33.el7_4 | RHSA-2018:0378 |
| Red Hat Software Collections for Red Hat Enterprise Linux 6 | rh-ruby24-ruby-0:2.4.2-86.el6 | RHSA-2017:3485 |
| Red Hat Software Collections for Red Hat Enterprise Linux 6 | rh-ruby22-ruby-0:2.2.9-19.el6 | RHSA-2018:0583 |
| Red Hat Software Collections for Red Hat Enterprise Linux 6 | rh-ruby23-ruby-0:2.3.6-67.el6 | RHSA-2018:0585 |
Frequently Asked Questions
Is GHSA-mqwr-4qf2-2hcv in your dependencies?
O3 Security finds GHSA-mqwr-4qf2-2hcv across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.