Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage
- Exploited
- No known exploitation
- Fix
- Fixed in 8.1.4.1, 8.0.5.2
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 8.1.4.1, 8.0.5.2.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 39/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Active Storage in Rails applications that store files in Google Cloud Storage and accept direct uploads can be abused by a remote attacker, without logging in, to upload files larger than the size they declared. This can store oversized files and bypass application file size validations and quotas.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach17/20Affects Ruby on Rails (a widely deployed server, runtime, framework or database)
- Severity5.3/10CVSS 5.3
- No patch0/5No signal
What would change the score
- Would score about 84 if added to CISA KEV
- Would score about 79 if CISA's SSVC rates exploitation active
- Would score about 44 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 8.1.4.1, 8.0.5.2.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126085 (Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126085 (entry last updated 2026-11-10): Affected: - rails rails: from 8.1, fixed in 8.1.4.1; fixed in 8.0.5.2 - RubyGems package activestorage: from 8.1.0.beta1, fixed in 8.1.4.1 - RubyGems package activestorage: fixed in 8.0.5.2 Fixed versions: 8.1.4.1, 8.0.5.2. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126085 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126085 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Packages (RubyGems): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies. - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/rails/rails/security/advisories/GHSA-hfr4-8rjc-97m2 - 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 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126085 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126085.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- rails rails
From 8.1 · fixed in 8.1.4.1; fixed in 8.0.5.2
- activestorageRubyGems
From 8.1.0.beta1 · fixed in 8.1.4.1
- activestorageRubyGems
fixed in 8.0.5.2
Evidence 7
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 4
- Repository
- Repository
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126085
Is CVE-2026-126085 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-126085?
rails: from 8.1 before 8.1.4.1; before 8.0.5.2. activestorage (RubyGems): from 8.1.0.beta1 before 8.1.4.1. activestorage (RubyGems): before 8.0.5.2.Source: cve.now feed data
How do I fix CVE-2026-126085?
Upgrade to a fixed version: 8.1.4.1, 8.0.5.2.Source: cve.now feed data