How severe is CVE-2020-15237?

CVE-2020-15237 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-15237?

CVE-2020-15237 affects the following packages: shrine (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2020-15237?

Update shrine to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15237 is resolved across your whole dependency graph.

How do I detect CVE-2020-15237 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shrine, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-15237 if there is no patch (or I can't update yet)?

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.

Is CVE-2020-15237 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-15237 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-15237?

CVE-2020-15237 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 62th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-15237?

CVE-2020-15237 is classified as CWE-203 (CWE-203), CWE-208 (CWE-208). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-15237 published, and has it been updated?

CVE-2020-15237 was published on October 5, 2020 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2020-15237 — shrine

MEDIUMFix: shrinerb/shrine@1b27090

CVE-2020-15237 is a medium-severity (CVSS 5.9) CWE-203 vulnerability in shrine. A fix is available for shrine — see the affected versions and patch details below.

Possible timing attack in derivation_endpoint

Also known asGHSA-5jjv-x4fq-qjwp

Published

Oct 5, 2020

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs62th percentile — riskier than 62% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-15237 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

💎shrine

Real-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

Impact

When using the derivation_endpoint plugin, it's possible for the attacker to use a timing attack to guess the signature of the derivation URL.

Patches

The problem has been fixed by comparing sent and calculated signature in constant time, using Rack::Utils.secure_compare. Users using the derivation_endpoint plugin are urged to upgrade to Shrine 3.3.0 or greater.

Workarounds

Users of older Shrine versions can apply the following monkey-patch after loading the derivation_endpoint plugin:

class Shrine
  class UrlSigner
    def verify_signature(string, signature)
      if signature.nil?
        fail InvalidSignature, "missing \"signature\" param"
      elsif !Rack::Utils.secure_compare(signature, generate_signature(string))
        fail InvalidSignature, "provided signature does not match the calculated signature"
      end
    end
  end
end

References

You can read more about timing attacks here.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`shrine`	all versions	3.3.0`bundle update shrine --conservative`

Affected Products

1 product · 1 configurations

Application

shrineshrinerb

< 3.3.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shrine, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update shrine to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15237 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.

Frequently Asked Questions

### Impact When using the `derivation_endpoint` plugin, it's possible for the attacker to use a timing attack to guess the signature of the derivation URL. ### Patches The problem has been fixed by comparing sent and calculated signature in constant time, using `Rack::Utils.secure_compare`. Users using the `derivation_endpoint` plugin are urged to upgrade to Shrine 3.3.0 or greater. ### Workarounds Users of older Shrine versions can apply the following monkey-patch after loading the `derivation_endpoint` plugin: ```rb class Shrine class UrlSigner def verify_signature(string, signat