CVE-2026-52681
Received Received - Intake

Sieve Script CPU Limit Bypass in Open-Xchange

Publication date: 2026-08-28

Last updated on: 2026-08-28

Assigner: Open-Xchange

Description
Sieve CPU resource usage is tracked in the compiled script, so an attacker that has valid credentials can reset the accounting by repeatedly changing the active script. Compiled script files are also not removed when a script is deleted or renamed. The configured Sieve CPU limit can be bypassed, allowing sustained CPU consumption, and the leftover files increase disk consumption. Both can cause degradation of service for mail delivery. Monitor system for abnormal CPU usage and disk consumption. Update to non-vulnerable version. No publicly available exploits are known.

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Meta Information

Published
2026-08-28
Last Modified
2026-08-28
Generated
2026-08-28
AI Q&A
2026-08-28
EPSS Evaluated
N/A
NVD
CVE-2026-52681
EUVD
EUVD-2026-67678

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-1050 The product has a loop body or loop condition that contains a control element that directly or indirectly consumes platform resources, e.g. messaging, sessions, locks, or file descriptors.

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Executive Summary

This vulnerability involves Sieve CPU resource tracking in compiled scripts. An attacker with valid credentials can reset CPU usage accounting by repeatedly changing the active script. Compiled script files are not deleted when scripts are removed or renamed, allowing CPU limits to be bypassed. This leads to sustained high CPU usage and increased disk consumption, degrading mail delivery performance.

Detection Guidance

Monitor system CPU usage and disk consumption for abnormal activity. Check for leftover compiled script files in Sieve-related directories. No specific commands are provided in the context.

Impact Analysis

This vulnerability can cause service degradation for mail delivery due to sustained high CPU usage and increased disk consumption. Attackers may exploit it to consume excessive system resources, potentially leading to slower performance or downtime for email services.

Mitigation Strategies

Update to a non-vulnerable version of the software. Remove or clean up leftover compiled script files. Monitor and limit CPU usage for Sieve processes.

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