Possible timing attack in derivation_endpoint

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2020-15237: 1.01% estimated exploitation activity in the next 30 days; percentile 63.33 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact When using the derivationendpoint 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.securecompare. Users using the derivationendpoint 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 derivationendpoint plugin: References You can read more about timing attacks here.

Published by the source

5 Oct 2020, 15:48 UTC

Last modified by the source

16 May 2023, 16:18 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5jjv-x4fq-qjwp

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# Patch Next advisory brief: CVE-2020-15237

Advisory: Possible timing attack in derivation_endpoint
IDs: CVE-2020-15237, GHSA-5jjv-x4fq-qjwp
Record: https://patchnext.com/advisories/cve-2020-15237 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: shrine 3.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems shrine: affected < 3.3.0; fixed in 3.3.0

## Suggested inspection (read-only)
- RubyGems shrine: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on shrine.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5jjv-x4fq-qjwp (GitHub-reviewed advisory GHSA-5jjv-x4fq-qjwp lists affected ranges: RubyGems shrine >=0 <3.3.0)

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