CVE-2026-45377 is a medium-severity (CVSS 6.5) Information Exposure vulnerability in decidim-core. A fix is available for decidim-core — see the affected versions and patch details below.
Decidim: Private exports can be downloaded through reusable links
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45377.
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
CVE-2026-45377 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% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
decidim-core💎decidim-core💎decidim-coreReal-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
Description
The normal download_your_data flow requires the requester to be logged in as the export owner, but the resulting Active Storage blob redirect URL can be replayed without authentication by anyone who obtains it.
Technical description
This private export flow turns an authenticated, user-scoped download into a reusable bearer link because the protected Decidim endpoint redirects to the underlying Active Storage blob URL. Decidim::DownloadYourDataController#download_file correctly scopes the export record to current_user, so the wrapper route itself is not directly accessible to another user. However, once the owner
performs that authenticated GET request, the response redirects to a signed Active Storage URL that is no longer bound to the user session. Anyone who learns that URL can replay it and retrieve the file without being logged in as the export owner.
Because the blob redirect URL is delivered through a GET request and appears in the redirect chain, it is more likely to leak through browser history, logs, proxy tooling, screenshots, copied links, support transcripts, or other client-side handling of URLs.
Reproduction steps:
Step 1. Generate or locate a completed export in the Web UI.
- Sign in as
[email protected]athttp://localhost:3001/users/sign_in. - Open
http://localhost:3001/download_your_data. - Request a new export from the page and wait until the export becomes downloadable.
- Open the completed export entry from the list and copy its wrapper URL, for example
http://localhost:3001/download_your_data/download?uuid=07286e61-932d-46d4-bd74-bcd1340c503f.
Step 2. Download through the authenticated wrapper route.
- While still signed in as [email protected], open the wrapper URL in the browser.
- Confirm that this Decidim route requires the owner session and is not directly usable when logged out or when logged in as another user.
Step 3. Capture the final bearer URL in the redirect chain.
- In DevTools Network or Burp, inspect the redirect sequence for the wrapper request.
- Copy the Active Storage redirect URL, typically matching
http://localhost:3001/rails/active_storage/blobs/redirect/<SIGNED_ID>/<FILENAME>. - Note that the Active Storage redirect URL is no longer protected by the Decidim ownership check.
Step 4. Replay the final file URL without authentication.
- Open a private window or separate browser with no Decidim session.
- Paste the copied
http://localhost:3001/rails/active_storage/blobs/redirect/<SIGNED_ID>/<FILENAME>URL. - Confirm the export file still downloads even though you are not logged in as the export owner.
Impact
Personal data exports can be retrieved through leakage channels such as browser history, logs, referrers, screenshots, copied links, support transcripts, intercepted email content, or other client-side disclosure of the GET URL.
Patches
See https://github.com/decidim/decidim/pull/16680
Workarounds
Disable Private Downloads URLs
Reference
OWASP A01:2021 Broken Access Control
Credits
This issue was discovered in a security audit organized by the Decidim Association and made by Radically Open Security against Decidim financed by NGI.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | decidim-core | all versions | 0.30.9bundle update decidim-core --conservative |
| 💎RubyGems | decidim-core | ≥ 0.31.0.rc1&&< 0.31.5 | 0.31.5bundle update decidim-core --conservative |
| 💎RubyGems | decidim-core | ≥ 0.32.0.rc1&&< 0.32.0 | 0.32.0bundle update decidim-core --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for decidim-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update decidim-core to 0.30.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45377 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 CVE-2026-45377 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-45377. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-45377 in your dependencies?
O3 Security finds CVE-2026-45377 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.