CVE-2026-61911Network attack vector

Authenticated mailbox metadata disclosure via Sieve oracle

Published Sep 9, 2026 · Updated Sep 10, 2026

Information disclosure in Cyrus IMAP 3.11.0 through 3.12.3 allows remote authenticated users to probe private mailboxes via Sieve. The same flaw affects versions before 3.8.8 and 3.9.0 through 3.10.3; during LMTP delivery, the Sieve engine exposes mailbox or shared-annotation lookup results through the fileinto branch that fires. Reaching the oracle requires a valid account, permission to install a Sieve script, and LMTP delivery; it reveals mailbox existence or annotation values without message contents.

CVSS severity4.3
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

Information disclosure in Cyrus IMAP 3.11.0 through 3.12.3 allows remote authenticated users to probe private mailboxes via Sieve. The same flaw affects versions before 3.8.8 and 3.9.0 through 3.10.3; during LMTP delivery, the Sieve engine exposes mailbox or shared-annotation lookup results through the fileinto branch that fires. Reaching the oracle requires a valid account, permission to install a Sieve script, and LMTP delivery; it reveals mailbox existence or annotation values without message contents.

The record

CVE
CVE-2026-61911
Published
Sep 9, 2026
Updated
Sep 10, 2026
Vendor
Project Cyrus
Product
Cyrus IMAP
Classifications
CWE-497, CAPEC-170, CAPEC-694, T1087.003
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

4.3MITRECVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

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-497Exposure of Sensitive System Information to an Unauthorized Control Sphere
CAPEC-170Web Application Fingerprinting
CAPEC-694System Location Discovery
T1087.003Email Account

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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