stalwartlabs stalwart up to 0.13.2 allocation of resources

Summaryinfo

A vulnerability was found in stalwartlabs stalwart up to 0.13.2. It has been classified as problematic. The impacted element is an unknown function. Performing a manipulation results in allocation of resources. This vulnerability is reported as CVE-2025-59045. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, was found in stalwartlabs stalwart up to 0.13.2. This affects an unknown code block. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. The summary by CVE is:

Stalwart is a mail and collaboration server. Starting in version 0.12.0 and prior to version 0.13.3, a memory exhaustion vulnerability exists in Stalwart's CalDAV implementation that allows authenticated attackers to cause denial-of-service by triggering unbounded memory consumption through recurring event expansion. An authenticated attacker can crash the Stalwart server by creating recurring events with large payloads and triggering their expansion through CalDAV REPORT requests. A single malicious request expanding 300 events with 1000-character descriptions can consume up to 2 GB of memory. The vulnerability exists in the `ArchivedCalendarEventData.expand` function, which processes CalDAV `REPORT` requests with event expansion. When a client requests recurring events in their expanded form using the `` element, the server stores all expanded event instances in memory without enforcing size limits. Users should upgrade to Stalwart version 0.13.3 or later to receive a fix. If immediate upgrading is not possible, implement memory limits at the container/system level; monitor server memory usage for unusual spikes; consider rate limiting CalDAV REPORT requests; and restrict CalDAV access to trusted users only.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2025-59045 since 09/08/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 0.13.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 15762fba2ba335e560b8d25f71af085a8b6b6cf2 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• stalwartlabs

Name

• stalwart

Version

• 0.13.0
• 0.13.1
• 0.13.2

License

• open-source

Website

• Product: https://github.com/stalwartlabs/stalwart/

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CPE 2.2info

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