CVE-2026-61915Network attack vector

Authenticated CalDAV worker crash via selector double-free

Published Sep 9, 2026 · Updated Sep 10, 2026

Double-free in affected Cyrus IMAP releases allows remote authenticated users to crash a CalDAV worker via a crafted PATCH request. The VPATCH BYPARAM loop frees the selector during each matched-property iteration, so multiple matching properties free the same memory twice. A valid calendar account, enabled CalDAV, and a resource with at least two matching properties are required; the observed consequence is termination of one worker.

CVSS severity4.2
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free in affected Cyrus IMAP releases allows remote authenticated users to crash a CalDAV worker via a crafted PATCH request. The VPATCH BYPARAM loop frees the selector during each matched-property iteration, so multiple matching properties free the same memory twice. A valid calendar account, enabled CalDAV, and a resource with at least two matching properties are required; the observed consequence is termination of one worker.

The record

CVE
CVE-2026-61915
Published
Sep 9, 2026
Updated
Sep 10, 2026
Vendor
Project Cyrus
Product
Cyrus IMAP
Classifications
CWE-415, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.8.8
  2. Affected versionversion=3.11.0 <3.12.4
  3. Affected versionversion=3.9.0 <3.10.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Project Cyrus · Cyrus IMAPversion=0 <3.8.8; version=3.11.0 <3.12.4; version=3.9.0 <3.10.4

Published CVSS scores

4.2MITRE CNACVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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