CVE-2026-24900VulnerabilityPublished 9 Feb 2026

CVE-2026-24900: MarkUsProject Markus · Insecure Direct Object Reference

Affects MarkUsProject MarkusSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.9.1 when convenient.

Data as of 25 Oct 2026, 19:02 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 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.9.1

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

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

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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Feb 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 2026-10-25.

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 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 MarkUsProject Markus to 2.9.1.

Affected software

Product	Affected	Fixed in
MarkUsProjectMarkus	Affected <2.9.1	Fixed in 2.9.1

AI-suggested

1. Immediate upgrade of all Markus instances to version 2.9.1 or later, where the vulnerability is fixed. 2. Conduct an access control audit to verify that submission file access is correctly scoped to authenticated users. 3. Implement enhanced logging and monitoring of file access requests, focusing on unusual patterns such as access to files outside a user's courses or assignments. 4. Enforce strong authentication mechanisms and consider multi-factor authentication to reduce risk of account compromise. 5. Educate users and administrators about the risks of unauthorized data access and encourage prompt reporting of suspicious activity. 6. Review and update privacy policies and data handling procedures to ensure compliance with GDPR and other relevant regulations. 7. If immediate patching is not feasible, consider temporary network segmentation or access restrictions to limit exposure of the vulnerable endpoints. 8.

Description

CVE-2026-24900 is an authorization bypass vulnerability in MarkUsProject's Markus web application versions prior to 2.9.1. The flaw allows authenticated users with limited privileges to access arbitrary student submission files by manipulating the select_file_id parameter, which was not properly scoped to the requesting user. This vulnerability impacts confidentiality by exposing sensitive student assignment data without proper authorization. Exploitation requires authentication but no user interaction beyond crafted requests. The vulnerability has a CVSS score of 6.5 (medium severity) and does not affect integrity or availability. The issue is fixed in version 2.9.

Impact

For European organizations, particularly universities and educational institutions using Markus versions prior to 2.9.1, this vulnerability poses a significant risk to the confidentiality of student data. Unauthorized access to submission files could lead to exposure of sensitive academic work, personal information, and potentially intellectual property. Such data breaches may result in reputational damage, loss of trust, and regulatory penalties under GDPR due to improper handling of personal data. Although the vulnerability does not affect data integrity or system availability, the confidentiality breach alone is critical in the academic context. The ease of exploitation (network accessible, low complexity) combined with the requirement for authenticated access means insider threats or compromised accounts could leverage this flaw. European institutions with large student populations and extensive use of Markus are at higher risk, especially if patching is delayed. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits given the public disclosure.

CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (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 17 Feb 2026, 09:42 UTC

WeaknessesCWE-639

Technical details

References

Community reviews

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