VulnerabilityPublished 24 Mar 2026

CVE-2026-30662: DoS

Source CVE Database V5

Not known to be exploited · CVSS 6.5 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

AI-suggested

To mitigate this vulnerability, organizations should: 1) Restrict bulk download functionality to trusted users and monitor for unusual download patterns indicative of abuse. 2) Implement rate limiting or throttling on bulk download requests to prevent excessive memory consumption. 3) Configure PHP memory limits and PHP-FPM process management settings to better handle resource exhaustion and enable graceful recovery. 4) Consider patching or upgrading ConcreteCMS to a version where this issue is resolved once an official fix is released. 5) If immediate patching is not possible, temporarily disable or restrict the file bulk download feature to reduce attack surface. 6) Employ web application firewalls (WAFs) to detect and block suspicious authenticated requests that attempt to exploit this vulnerability. 7) Conduct regular audits of user accounts and access privileges to minimize the risk of credential compromise. 8) Monitor server logs for repeated 500 errors or PHP-FPM crashes as indicators of attempted exploitation. These targeted actions go beyond generic advice by focusing on controlling resource usage, limiting access, and preparing for graceful failure handling.

Description

ConcreteCMS version 9.4.7 contains a Denial of Service (DoS) vulnerability in its File Manager component. The vulnerability arises from the 'download' method in 'concrete/controllers/backend/file.php', which improperly handles memory when creating zip archives by loading entire file contents into PHP memory. An authenticated attacker can exploit this by requesting bulk downloads of large files, causing an Out-Of-Memory (OOM) condition that crashes the PHP-FPM process and results in HTTP 500 errors. This vulnerability does not affect confidentiality or integrity but severely impacts availability. Exploitation requires authentication but no user interaction beyond sending the request. There are no known exploits in the wild currently, and no patches have been linked yet. The CVSS score is 6.

Impact

This vulnerability primarily impacts the availability of ConcreteCMS-based websites running version 9.4.7. An attacker with valid credentials can cause the PHP-FPM process to crash repeatedly by triggering Out-Of-Memory conditions through bulk download requests. This results in HTTP 500 errors, effectively causing denial of service to legitimate users and potentially disrupting business operations, customer access, and administrative functions. Organizations relying on ConcreteCMS for content management, especially those hosting large media files or offering bulk downloads, are at higher risk. The disruption could affect website uptime, degrade user experience, and increase operational costs due to recovery efforts. While confidentiality and integrity remain unaffected, the availability impact can be significant, especially for high-traffic or mission-critical sites. The requirement for authentication limits the attack surface but does not eliminate risk, as attackers may leverage compromised credentials or insider threats. No known exploits in the wild reduce immediate risk but do not preclude future exploitation. The lack of an official patch increases exposure until remediation is applied.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

wang1rrr.github.io/2026/02/11/CVE-Report-ConcreteCMS-DoS/ (opens in a new tab)

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 31 Mar 2026, 20:35 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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