UBUNTU-CVE-2026-42391 (CVE-2026-42391)
Vulnerability from osv_ubuntu – Published: 2026-08-28 00:00 – Updated: 2026-09-02 16:15 – Source website
VLAI
Details
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
Severity
7.5 (High)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
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{
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{
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},
{
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},
{
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},
{
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},
{
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},
{
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},
{
"binary_name": "dovecot-pop3d",
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},
{
"binary_name": "dovecot-sieve",
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},
{
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},
{
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},
{
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}
]
},
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"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",
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},
{
"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",
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{
"binary_name": "dovecot-pgsql",
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{
"binary_name": "dovecot-pop3d",
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},
{
"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"
}
]
},
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},
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"1:2.2.22-1ubuntu2.7",
"1:2.2.22-1ubuntu2.8",
"1:2.2.22-1ubuntu2.9",
"1:2.2.22-1ubuntu2.10",
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},
{
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},
{
"binary_name": "dovecot-gssapi",
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{
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{
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},
{
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},
{
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},
{
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{
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{
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{
"binary_name": "dovecot-sieve",
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},
{
"binary_name": "dovecot-solr",
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},
{
"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"
},
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{
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"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",
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]
},
{
"ecosystem_specific": {
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{
"binary_name": "dovecot-auth-lua",
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},
{
"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",
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{
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},
{
"binary_name": "dovecot-lucene",
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},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-mysql",
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},
{
"binary_name": "dovecot-pgsql",
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},
{
"binary_name": "dovecot-pop3d",
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{
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{
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},
{
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},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "mail-stack-delivery",
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}
]
},
"package": {
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},
{
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{
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{
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{
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{
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{
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{
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{
"binary_name": "dovecot-solr",
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},
{
"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": [
{
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{
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}
],
"type": "ECOSYSTEM"
}
],
"versions": [
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"1:2.3.16+dfsg1-3ubuntu2",
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"1:2.3.16+dfsg1-3ubuntu2.8",
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]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
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},
{
"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"
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{
"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": {
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"name": "dovecot",
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},
"ranges": [
{
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"versions": [
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},
{
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},
{
"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 unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.",
"id": "UBUNTU-CVE-2026-42391",
"modified": "2026-09-02T16:15:07Z",
"published": "2026-08-28T00:00:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-42391"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-42391"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-42391"
]
}
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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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