UBUNTU-CVE-2026-40017 (CVE-2026-40017)
Vulnerability from osv_ubuntu – Published: 2026-08-28 00:00 – Updated: 2026-09-02 16:15 – Source website
VLAI
Details
An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.
Severity
6.5 (Medium)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.9-1ubuntu2.6+esm4?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.1.7-7ubuntu3",
"1:2.2.9-1ubuntu1",
"1:2.2.9-1ubuntu2",
"1:2.2.9-1ubuntu2.1",
"1:2.2.9-1ubuntu2.3",
"1:2.2.9-1ubuntu2.4",
"1:2.2.9-1ubuntu2.5",
"1:2.2.9-1ubuntu2.6",
"1:2.2.9-1ubuntu2.6+esm1",
"1:2.2.9-1ubuntu2.6+esm2",
"1:2.2.9-1ubuntu2.6+esm3",
"1:2.2.9-1ubuntu2.6+esm4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.22-1ubuntu2.14"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.22-1ubuntu2.14?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.2.18-2ubuntu2",
"1:2.2.22-1ubuntu1",
"1:2.2.22-1ubuntu2",
"1:2.2.22-1ubuntu2.1",
"1:2.2.22-1ubuntu2.2",
"1:2.2.22-1ubuntu2.3",
"1:2.2.22-1ubuntu2.4",
"1:2.2.22-1ubuntu2.6",
"1:2.2.22-1ubuntu2.7",
"1:2.2.22-1ubuntu2.8",
"1:2.2.22-1ubuntu2.9",
"1:2.2.22-1ubuntu2.10",
"1:2.2.22-1ubuntu2.11",
"1:2.2.22-1ubuntu2.12",
"1:2.2.22-1ubuntu2.13",
"1:2.2.22-1ubuntu2.14"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.33.2-1ubuntu4.8?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.2.27-3ubuntu1",
"1:2.2.33.2-1ubuntu1",
"1:2.2.33.2-1ubuntu2",
"1:2.2.33.2-1ubuntu3",
"1:2.2.33.2-1ubuntu4",
"1:2.2.33.2-1ubuntu4.1",
"1:2.2.33.2-1ubuntu4.2",
"1:2.2.33.2-1ubuntu4.3",
"1:2.2.33.2-1ubuntu4.4",
"1:2.2.33.2-1ubuntu4.5",
"1:2.2.33.2-1ubuntu4.6",
"1:2.2.33.2-1ubuntu4.7",
"1:2.2.33.2-1ubuntu4.8"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.7.2-1ubuntu3.7?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.4.1-5ubuntu3",
"1:2.3.7.2-1ubuntu1",
"1:2.3.7.2-1ubuntu2",
"1:2.3.7.2-1ubuntu3",
"1:2.3.7.2-1ubuntu3.1",
"1:2.3.7.2-1ubuntu3.2",
"1:2.3.7.2-1ubuntu3.3",
"1:2.3.7.2-1ubuntu3.4",
"1:2.3.7.2-1ubuntu3.5",
"1:2.3.7.2-1ubuntu3.6",
"1:2.3.7.2-1ubuntu3.7"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.16+dfsg1-3ubuntu2.9?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.13+dfsg1-1ubuntu3",
"1:2.3.16+dfsg1-3ubuntu1",
"1:2.3.16+dfsg1-3ubuntu2",
"1:2.3.16+dfsg1-3ubuntu2.1",
"1:2.3.16+dfsg1-3ubuntu2.2",
"1:2.3.16+dfsg1-3ubuntu2.4",
"1:2.3.16+dfsg1-3ubuntu2.6",
"1:2.3.16+dfsg1-3ubuntu2.7",
"1:2.3.16+dfsg1-3ubuntu2.8",
"1:2.3.16+dfsg1-3ubuntu2.9"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.21+dfsg1-2ubuntu6.5?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.20+dfsg1-1ubuntu3",
"1:2.3.21+dfsg1-2ubuntu1",
"1:2.3.21+dfsg1-2ubuntu2",
"1:2.3.21+dfsg1-2ubuntu4",
"1:2.3.21+dfsg1-2ubuntu5",
"1:2.3.21+dfsg1-2ubuntu6",
"1:2.3.21+dfsg1-2ubuntu6.1",
"1:2.3.21+dfsg1-2ubuntu6.2",
"1:2.3.21+dfsg1-2ubuntu6.3",
"1:2.3.21+dfsg1-2ubuntu6.4",
"1:2.3.21+dfsg1-2ubuntu6.5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-flatcurve",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.4.2+dfsg1-3ubuntu2.1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.4.1+dfsg1-5ubuntu4",
"1:2.4.1+dfsg1-5ubuntu5",
"1:2.4.2+dfsg1-3ubuntu1",
"1:2.4.2+dfsg1-3ubuntu2",
"1:2.4.2+dfsg1-3ubuntu2.1"
]
}
],
"aliases": [],
"details": "An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.",
"id": "UBUNTU-CVE-2026-40017",
"modified": "2026-09-02T16:15:05Z",
"published": "2026-08-28T00:00:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-40017"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-40017"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-40017"
]
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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