CVE-2021-4304VulnerabilityPublished 5 Jan 2023Updated 28 May 2025

CVE-2021-4304: eprintsug ulcc-core · Command Injection

Affects eprintsug ulcc-coreSource CVE Database V5

Not known to be exploited · CVSS 6.3 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

6.3Medium

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

EPSS: 2.2% chance of exploitation in 30 days – higher than 82% 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:L/I:L/A:L

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

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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
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 on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Jan 2023
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

AI-suggested

European organizations should prioritize applying the official patch identified by commit 811edaae81eb044891594f00062a828f51b22cb1 to remediate the vulnerability. In addition to patching, organizations should implement strict access controls to limit who can authenticate and interact with the vulnerable component, employing multi-factor authentication to reduce the risk of credential compromise. Network segmentation should be enforced to isolate systems running eprintsug ulcc-core from broader enterprise networks, minimizing lateral movement opportunities. Monitoring and logging of command execution and authentication attempts on affected systems should be enhanced to detect anomalous activities indicative of exploitation attempts. Regular code audits and input validation improvements should be conducted to prevent similar injection vulnerabilities. Finally, organizations should maintain an incident response plan tailored to address command injection attacks, ensuring rapid containment and recovery.

Description

A vulnerability was found in eprintsug ulcc-core. It has been declared as critical. Affected by this vulnerability is an unknown functionality of the file cgi/toolbox/toolbox. The manipulation of the argument password leads to command injection. The attack can be launched remotely. The patch is named 811edaae81eb044891594f00062a828f51b22cb1. It is recommended to apply a patch to fix this issue. The associated identifier of this vulnerability is VDB-217447.

Impact

For European organizations utilizing eprintsug ulcc-core, particularly those deploying the vulnerable cgi/toolbox/toolbox component, this vulnerability poses a significant risk. Successful exploitation could lead to unauthorized command execution on critical servers, compromising confidentiality through data leakage, integrity via unauthorized modifications, and availability by disrupting services. Academic institutions, research centers, and digital repositories that rely on eprintsug software for managing electronic publications and archives may be especially vulnerable. Given the remote attack vector and absence of required user interaction, attackers could leverage this flaw to escalate privileges or move laterally within networks once initial access is obtained. Although exploitation requires some level of authentication, insider threats or compromised credentials could facilitate attacks. The medium CVSS score suggests moderate risk; however, the critical classification by the vendor indicates the potential for severe consequences if exploited in sensitive environments.

Summary

CVE-2021-4304 is a command injection vulnerability identified in the eprintsug ulcc-core software, specifically within an unspecified functionality of the file cgi/toolbox/toolbox. The vulnerability arises from improper handling of the 'password' argument, which can be manipulated by an attacker to inject arbitrary commands. This flaw allows remote attackers to execute system-level commands on the affected server without requiring user interaction, though some level of privileges (PR:L) is needed, indicating that the attacker must have some authenticated access. The vulnerability is classified under CWE-77, which pertains to improper neutralization of special elements used in a command ('Command Injection'). The CVSS v3.1 base score is 6.3, reflecting a medium severity level, with an attack vector of network (AV:N), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), unchanged scope (S:U), and impacts on confidentiality, integrity, and availability rated as low (C:L/I:L/A:L). No known exploits are currently reported in the wild, and a patch identified by commit 811edaae81eb044891594f00062a828f51b22cb1 has been released to remediate the issue. The vulnerability enables attackers with some level of access to execute arbitrary commands remotely, potentially leading to unauthorized data access, modification, or service disruption.

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection') (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #23OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
Architecture and Design
If at all possible, use library calls rather than external processes to recreate the desired functionality.
Implementation
If possible, ensure that all external commands called from the program are statically created.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
Attack patterns
LDAP Injection (opens in a new tab)
Command Delimiters (opens in a new tab)
IMAP/SMTP Command Injection (opens in a new tab)
Manipulating Writeable Terminal Devices (opens in a new tab)
Exploiting Multiple Input Interpretation Layers (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

Description

AI analysisMachine-generated, updated 7 Jul 2025, 09:26 UTC

WeaknessesCWE-77

Technical details

References

Community reviews

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