activestorage: Improper Neutralization of Special Elements in Output Used by a Downstream Component
CVE-2026-33202 is a critical-severity improper neutralization of special elements in output used by a downstream component vulnerability in activestorage from Rails, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected activestorage versions: >= 8.1.0.beta1, < 8.1.2.1; >= 8.0.0.beta1, < 8.0.4.1; < 7.2.3.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.69% chance of exploitation within 30 days, higher than 53% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Rails to 7.2.3.1 or 8.0.4.1 or 8.1.2.1, whichever matches your release line, or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Rails | activestorage | >= 8.1.0.beta1, < 8.1.2.1; >= 8.0.0.beta1, < 8.0.4.1; < 7.2.3.1 | Not stated |
| Rubyonrails | Rails | before 7.2.3.1; 8.0.0 up to, but not including, 8.0.4.1; 8.1.0 up to, but not including, 8.1.2.1 | 7.2.3.1, 8.0.4.1, 8.1.2.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.6 | Medium | CNA (github.com) |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official description
Active Storage allows users to attach cloud and local files in Rails applications. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, Active Storage's `DiskService#delete_prefixed` passes blob keys directly to `Dir.glob` without escaping glob metacharacters. If a blob key contains attacker-controlled input or custom-generated keys with glob metacharacters, it may be possible to delete unintended files from the storage directory. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements in Output Used by a Downstream Component
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
How developers prevent this class of flaw
- Programming languages and supporting technologies might be chosen which are not subject to these issues.
- Utilize an appropriate mix of allowlist and denylist parsing to filter control-plane syntax from all input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/rails/rails/commit/8c9676b803820110548cdb7523800db43bc6874c
- github.com/rails/rails/commit/955284d26e469a9c026a4eee5b21f0414ab0bccf
- github.com/rails/rails/commit/fa19073546360856e9f4dab221fc2c5d73a45e82
- github.com/rails/rails/releases/tag/v7.2.3.1Release Notes
- github.com/rails/rails/releases/tag/v8.0.4.1Release Notes
- github.com/rails/rails/releases/tag/v8.1.2.1Release Notes
Other vulnerabilities in activestorage
- 9.8 Critical severity
- 7.5 High severity
- 8.1 High severity
Recent Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 9.1 Critical severity
- 7.3 High severity
- 7.3 High severity
- 7.3 High severity
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