CVE-2024-23185VulnerabilityPublished 10 Sep 2024Updated 4 Nov 2025

CVE-2024-23185: Open-Xchange OX Dovecot Pro · Unthrottled Resource Allocation

Affects Open-Xchange OX Dovecot ProSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.2% chance of exploitation in 30 days – higher than 70% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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 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 2026-10-26.

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

Affected software

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

AI-suggested

To mitigate CVE-2024-23185, European organizations should implement strict header size restrictions at the mail transfer agent (MTA) level before emails reach Dovecot. Configuring MTAs like Postfix or Exim to reject or truncate emails with excessively large headers can prevent resource exhaustion. Administrators should monitor mail server logs for abnormal memory usage or unusually large emails appended by users. Applying any forthcoming patches from Open-Xchange GmbH promptly is essential once available. Additionally, enforcing user quotas and limiting the size of emails users can append reduces risk of self-inflicted DoS. Network-level protections such as rate limiting and anomaly detection on SMTP traffic can help identify and block suspicious large-header emails. Regularly auditing and updating mail server configurations to align with best practices for resource management will further reduce exposure. Finally, educating users about risks of appending large emails and monitoring for insider misuse can help prevent exploitation.

Description

Very large headers can cause resource exhaustion when parsing message. The message-parser normally reads reasonably sized chunks of the message. However, when it feeds them to message-header-parser, it starts building up "full_value" buffer out of the smaller chunks. The full_value buffer has no size limit, so large headers can cause large memory usage. It doesn't matter whether it's a single long header line, or a single header split into multiple lines. This bug exists in all Dovecot versions. Incoming mails typically have some size limits set by MTA, so even largest possible header size may still fit into Dovecot's vsz_limit. So attackers probably can't DoS a victim user this way. A user could APPEND larger mails though, allowing them to DoS themselves (although maybe cause some memory issues for the backend in general). One can implement restrictions on headers on MTA component preceding Dovecot. No publicly available exploits are known.

Impact

For European organizations using OX Dovecot Pro as their mail server, this vulnerability poses a significant risk to mail system availability. Although remote exploitation is limited by typical MTA size restrictions, insider threats or compromised user accounts could exploit the vulnerability by appending large emails, causing service disruptions or backend instability. This could impact business communications, delay critical email delivery, and increase operational costs due to system downtime or recovery efforts. Organizations with high email traffic or those relying heavily on Dovecot for mail storage and retrieval are particularly vulnerable. Additionally, memory exhaustion could lead to cascading failures affecting other services hosted on the same infrastructure. The lack of confidentiality or integrity impact reduces risk of data breach but does not diminish the operational impact. European entities in sectors such as finance, government, and healthcare, where email availability is critical, may face compliance and reputational risks if mail services are disrupted.

Summary

CVE-2024-23185 is a resource exhaustion vulnerability found in Open-Xchange GmbH's OX Dovecot Pro mail server software. The issue stems from the message-header-parser component, which constructs a "full_value" buffer by concatenating smaller chunks of email header data without enforcing any size limits. This means that if an email contains very large headers—either as a single long header line or a header split across multiple lines—the buffer can grow excessively large, leading to high memory consumption. The message-parser normally reads messages in reasonably sized chunks, but the unchecked aggregation in the header parser causes unbounded memory allocation. While mail transfer agents typically enforce size limits on incoming emails, mitigating the risk of remote exploitation, users who append large emails themselves can trigger this vulnerability, potentially causing denial-of-service (DoS) conditions by exhausting server memory. This can degrade backend performance or cause crashes. The vulnerability affects all versions of Dovecot, as no version-specific fixes are noted. No public exploits have been reported, and no patches have been linked yet. The CVSS 3.1 base score is 7.5, reflecting a high severity due to the vulnerability's impact on availability, ease of exploitation (no privileges or user interaction required), and network attack vector.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 17:04 UTC

Technical details

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