VulnerabilityPublished 23 Mar 2026

CVE-2026-33173: rails activestorage · Improper Verification of Intent by Broadcast Receiver

Affects rails activestorageSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium · fixed in 8.1.2.1 : update rails activestorage when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 8.1.2.1, 8.0.4.1, 7.2.3.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade rails activestorage to 8.1.2.1, 8.0.4.1 or 7.2.3.1.

Affected software

Product	Affected	Fixed in
railsactivestorage	Affected >=8.1.0.beta1 <8.1.2.1	Fixed in 8.1.2.1
railsactivestorage	Affected >=8.0.0.beta1 <8.0.4.1	Fixed in 8.0.4.1
railsactivestorage	Affected <7.2.3.1	Fixed in 7.2.3.1

AI-suggested

To mitigate this vulnerability, organizations should immediately upgrade Rails Active Storage to versions 8.1.2.1, 8.0.4.1, or 7.2.3.1 or later, where the issue is patched. Beyond upgrading, developers should implement additional server-side validation of uploaded files independent of Active Storage's automatic MIME detection. This includes verifying file content types using trusted libraries or services, restricting allowed file types and sizes, and scanning uploads for malware. Employing Content Security Policy (CSP) headers and isolating uploaded files in non-executable directories can reduce the risk of malicious file execution. Logging and monitoring upload activities for anomalies can help detect exploitation attempts. If immediate upgrading is not feasible, temporarily disabling direct uploads or restricting upload functionality to trusted users can reduce exposure. Regularly reviewing and updating dependencies and maintaining a secure development lifecycle will help prevent similar issues.

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, `DirectUploadsController` accepts arbitrary metadata from the client and persists it on the blob. Because internal flags like `identified` and `analyzed` are stored in the same metadata hash, a direct-upload client can set these flags to skip MIME detection and analysis. This allows an attacker to upload arbitrary content while claiming a safe `content_type`, bypassing any validations that rely on Active Storage's automatic content type identification. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

Impact

This vulnerability can have significant impacts on organizations using affected versions of Rails Active Storage. By bypassing MIME type detection, attackers can upload malicious files disguised as safe content types, potentially leading to malware distribution, unauthorized code execution, or defacement if the files are served or processed without additional validation. This undermines the integrity of file upload controls and can facilitate further exploitation chains, especially in web applications that rely heavily on Active Storage for handling user-uploaded content. The ability to upload arbitrary content without proper validation increases the risk of server compromise, data leakage, or service disruption. Organizations with public-facing file upload features are particularly at risk, as attackers can exploit this vulnerability remotely over the network without authentication. The medium severity rating indicates a moderate risk, but the actual impact depends on how the uploaded files are used or processed downstream in the application environment.

CWE-925Improper Verification of Intent by Broadcast Receiver (opens in a new tab)
Variant weakness
The Android application uses a Broadcast Receiver that receives an Intent but does not properly verify that the Intent came from an authorized source.
Architecture and Design
Before acting on the Intent, check the Intent Action to make sure it matches the expected System action.
OWASP ASVS 4.0.3
V1.14.1 (opens in a new tab)
V14.5.2 (opens in a new tab)
V14.5.3 (opens in a new tab)
Attack patterns
Android Intent Intercept (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Mar 2026, 00:03 UTC

WeaknessesCWE-925

Technical details

References

Community reviews

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