CVE-2026-126085 (CVSS 5.3)

Description

Active Storage makes it simple to upload and reference files in cloud services and attach those files to Active Record objects. Prior to 8.1.4.1 and 8.0.5.2, ActiveStorage::Service::GCSService#url_for_direct_upload does not bind the declared content length into the signed direct-upload URL, and #headers_for_direct_upload returns no length constraint, so the URL authorizes an upload body of any size. A direct-upload client could store a file larger than the byte_size it declared, and the resulting blob keeps the declared size, possibly bypassing application file size validations and quotas. This is the weakness that CVE-2020-8162 fixed in the S3 service. Applications that store files in Google Cloud Storage and accept direct uploads are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0048

Probability of exploitation

0.42%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-602 CWE-602

References

Other References

https://github.com/rails/rails/commit/7fe85a72a789eae5ee070ce3ee1dad10a8a5f70c https://github.com/rails/rails/commit/e19916cea31cbfb0030b165ae853b741f8dd57a7 https://github.com/rails/rails/releases/tag/v8.0.5.2 https://github.com/rails/rails/releases/tag/v8.1.4.1 https://github.com/rails/rails/security/advisories/GHSA-hfr4-8rjc-97m2

Frequently Asked Questions

What is CVE-2026-126085? +

Active Storage makes it simple to upload and reference files in cloud services and attach those files to Active Record objects. Prior to 8.1.4.1 and 8.0.5.2, ActiveStorage::Service::GCSService#url_for_direct_upload does not bind the declared content length into the signed direct-upload URL, and #headers_for_direct_upload returns no length constraint, so the URL authorizes an upload body of any size. A direct-upload client could store a file larger than the byte_size it declared, and the resulting blob keeps the declared size, possibly bypassing application file size validations and quotas. This is the weakness that CVE-2020-8162 fixed in the S3 service. Applications that store files in Google Cloud Storage and accept direct uploads are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-126085? +

CVE-2026-126085 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0048, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-126085? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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