VulnerabilityPublished 10 Sep 2024Updated 4 Nov 2025

CVE-2024-23184: Open-Xchange OX Dovecot Pro · Unthrottled Resource Allocation

Affects Open-Xchange OX Dovecot ProSource CVE Database V5

Not known to be exploited · CVSS 5.0 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.0Medium

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 57% 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:C/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: Low
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: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within 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: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Sep 2024
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

Affected software

Product	Affected	Fixed in
Open-Xchange GmbH OX Dovecot Pro	Affected =0	Fixed in–

AI-suggested

To mitigate CVE-2024-23184 effectively, organizations should implement strict limits on the number of address headers allowed in incoming emails at the mail transfer agent (MTA) level, such as Postfix, Exim, or Sendmail, before messages reach OX Dovecot Pro. This can be done by configuring header size and count restrictions or employing filtering rules to reject or quarantine suspicious emails with abnormally large header counts. Monitoring email traffic for unusual patterns in header counts can provide early detection of exploitation attempts. Additionally, organizations should ensure their OX Dovecot Pro installations are updated promptly once patches become available from Open-Xchange GmbH. Network-level protections such as rate limiting and connection throttling on SMTP ports can reduce the volume of potentially malicious emails. Deploying email security gateways with advanced filtering capabilities can also help block malformed or suspicious emails. Finally, maintaining comprehensive logging and alerting on mail server performance metrics will aid in identifying resource exhaustion events early and enable rapid incident response.

Description

Having a large number of address headers (From, To, Cc, Bcc, etc.) becomes excessively CPU intensive. With 100k header lines CPU usage is already 12 seconds, and in a production environment we observed 500k header lines taking 18 minutes to parse. Since this can be triggered by external actors sending emails to a victim, this is a security issue. An external attacker can send specially crafted messages that consume target system resources and cause outage. One can implement restrictions on address headers on MTA component preceding Dovecot. No publicly available exploits are known.

Impact

For European organizations, this vulnerability poses a risk primarily to the availability of email services. Organizations relying on OX Dovecot Pro for mail delivery and storage could experience service degradation or outages if targeted by attackers sending emails with excessively large numbers of address headers. This could disrupt business communications, lead to operational downtime, and impact productivity. Critical sectors such as finance, government, healthcare, and large enterprises with high email traffic volumes are particularly vulnerable to service interruptions. Since the attack vector is external email delivery, organizations with public-facing mail servers are at risk. The vulnerability does not compromise data confidentiality or integrity but can cause denial-of-service conditions that may require emergency response and incident handling. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time. European organizations must consider this vulnerability in their risk assessments and incident response planning to maintain email service continuity.

Summary

CVE-2024-23184 is a resource exhaustion vulnerability in Open-Xchange GmbH's OX Dovecot Pro, a widely used mail server software. The issue stems from the software's handling of email address headers—specifically, when an email contains an unusually large number of address header lines such as From, To, Cc, and Bcc. Parsing these headers is CPU intensive; tests show that 100,000 header lines can cause 12 seconds of CPU usage, while 500,000 lines can take up to 18 minutes to parse. This excessive processing can be triggered remotely by sending crafted emails to the target system, leading to denial-of-service (DoS) conditions by exhausting CPU resources. The vulnerability does not affect confidentiality or integrity but impacts availability. It requires no user interaction and can be exploited remotely without authentication, increasing its risk profile. No public exploits have been reported yet, but the vulnerability is recognized and published with a CVSS 3.1 base score of 5.0 (medium severity). Mitigation involves implementing restrictions on the number of address headers at the mail transfer agent (MTA) level before the email is processed by Dovecot, effectively limiting resource consumption. This approach is necessary because the vulnerability lies in the parsing logic of Dovecot Pro itself. The vulnerability was reserved in January 2024 and published in September 2024, indicating recent discovery and disclosure.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 17:03 UTC

Technical details

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