Bug 2525559 (CVE-2026-40019)

Summary: CVE-2026-40019 dovecot: Dovecot: Denial of Service via truncated quoted argument in ManageSieve
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in Dovecot's ManageSieve login process. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted, truncated quoted argument. This action causes the process to enter an infinite loop, consuming excessive CPU resources. Repeated exploitation can lead to a denial of service, impacting Sieve script management and overall server availability.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2526679    
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Description OSIDB Bzimport 2026-08-28 11:22:51 UTC 
An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which makes it spin in an infinite loop consuming CPU. This can cause degradation or denial of service for Sieve script management, and repeated connections can consume all available CPU on the server. Monitor system for abnormal CPU usage and kill the offending process. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.
Comment 2 Jon Orris 2026-10-06 16:11:13 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:76763 https://access.redhat.com/errata/RHSA-2026:76763
Comment 3 Jon Orris 2026-10-08 17:41:37 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:79371 https://access.redhat.com/errata/RHSA-2026:79371
Comment 4 Jon Orris 2026-10-12 14:57:06 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:80825 https://access.redhat.com/errata/RHSA-2026:80825