CVE-2026-27857

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So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. 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Please update the affected package as soon as possible."}], "x_adpType": "supplier", "x_generator": {"engine": "sadp-cli 1.0.0"}, "providerMetadata": {"orgId": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "shortName": "redhat-SADP", "dateUpdated": "2026-07-15T01:12:47.787Z"}}]}}

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{"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/a:redhat:rhel_eus:9.4"], "defaultStatus": "affected", "packageName": "dovecot", "product": "Red Hat Enterprise Linux 9.4 Extended Update Support", "vendor": "Red Hat", "versions": [{"lessThan": "*", "status": "unaffected", "version": "1:2.3.16-11.el9_4.2", "versionType": "rpm"}]}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/a:redhat:rhel_eus:9.6"], "defaultStatus": "affected", "packageName": "dovecot", "product": "Red Hat Enterprise Linux 9.6 Extended Update Support", "vendor": "Red Hat", "versions": [{"lessThan": "*", "status": "unaffected", "version": "1:2.3.16-15.el9_6.1", "versionType": "rpm"}]}, {"collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": ["cpe:/o:redhat:enterprise_linux:6"], "defaultStatus": "affected", "packageName": "dovecot", "product": "Red Hat Enterprise Linux 6", "vendor": "Red Hat"}], "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*", "matchCriteriaId": "BE209329-C5EA-4EE7-A23E-CD2EC061A9A4", "versionEndExcluding": "2.4.3", "vulnerable": true}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "matchCriteriaId": "5CF82590-D98A-4E06-AC8C-6CC3506ED923", "versionEndExcluding": "2.3.22.1", "vulnerable": true}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "matchCriteriaId": "8476287B-40B2-4533-A3AB-B880516C0B5C", "versionEndExcluding": "3.0.5", "versionStartIncluding": "3.0.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "matchCriteriaId": "11CA35AA-72CB-4614-A064-8A90F65D8A71", "versionEndExcluding": "3.1.4", "versionStartIncluding": "3.1.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Sending \"NOOP (((...)))\" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known."}, {"lang": "es", "value": "El env\u00edo del comando \u2019NOOP (((...)))\u2019 con 4000 par\u00e9ntesis abiertos+cerrados resulta en un uso de memoria adicional de ~1MB. Comandos m\u00e1s largos resultar\u00e1n en la desconexi\u00f3n del cliente. Este 1 MB puede dejarse asignado por per\u00edodos de tiempo m\u00e1s prolongados al no enviar el LF de terminaci\u00f3n del comando. As\u00ed, un atacante podr\u00eda conectarse posiblemente incluso desde una \u00fanica IP y crear 1000 conexiones para asignar 1 GB de memoria, lo que probablemente resultar\u00eda en alcanzar el l\u00edmite de VSZ y matar el proceso y sus otras conexiones proxy. Un atacante podr\u00eda conectarse posiblemente incluso desde una \u00fanica IP y crear 1000 conexiones para asignar 1 GB de memoria, lo que probablemente resultar\u00eda en alcanzar el l\u00edmite de VSZ y matar el proceso y sus otras conexiones proxy. Instale la versi\u00f3n corregida, no hay otra remediaci\u00f3n. No se conocen exploits disponibles p\u00fablicamente."}], "id": "CVE-2026-27857", "lastModified": "2026-10-26T22:10:00.163", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 4.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 1.4, "source": "security@open-xchange.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-27857", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-03-27T12:39:00.311649Z", "version": "2.0.3"}}]}, "published": "2026-03-27T09:16:19.917", "references": [{"source": "security@open-xchange.com", "tags": ["Vendor Advisory"], "url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:13498"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:13830"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:13857"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:17602"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:17625"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:17626"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:17628"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:17630"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:18053"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:19149"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:19364"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:19453"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:19455"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:26564"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/security/cve/CVE-2026-27857"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2452179"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27857.json"}], "sourceIdentifier": "security@open-xchange.com", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-400"}], "source": "security@open-xchange.com", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-770"}], "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}]}

{"bugzilla": {"description": "dovecot: denial of service via specially crafted NOOP command", "id": "2452179", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2452179"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-770", "details": ["Sending \"NOOP (((...)))\" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.", "A flaw was found in dovecot. An unauthenticated and remote attacker can send a specially crafted \"NOOP\" command containing numerous open and close parentheses without a command-ending line feed, causing the server to allocate an excessive amount of memory, resulting in a denial of service."], "mitigation": {"lang": "en:us", "value": "Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible."}, "name": "CVE-2026-27857", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Affected", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "dovecot", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-03-27T08:10:20Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-27857\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-27857\nhttps://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json"], "statement": "This flaw allows an unauthenticated and remote attacker to cause a denial of service via a specially crafted \"NOOP\" command. Due to this reason, this vulnerability has been rated with an important severity.", "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.3.0]"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "OX Dovecot Pro", "source": "cna", "vendor": "Open-Xchange GmbH"}, "product": "ox_dovecot_pro", "vendor": "open-xchange"}], "analysis": {"en": {"generated_at": "2026-03-28T13:29:42.626183+00:00", "value": {"mitigation_remediation": ["Apply vendor patch for OX Dovecot Pro", "Verify that the updated version is deployed on all affected servers", "Continue to monitor for any related advisories or exploit activity"], "summary": {"action": "Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "The vulnerability affects Open-Xchange GmbH\u2019s OX Dovecot Pro product. No version specifics are provided, so all releases of the affected product are considered at risk until a patched version is applied.", "description_and_impact": "A specially crafted NOOP command containing thousands of parentheses can cause the Dovecot server to allocate approximately one megabyte of memory per connection. When an attacker sends multiple such commands without terminating the line, the memory allocated persists, potentially exhausting the server\u2019s virtual address space. The result is the termination of the server process and disruption of all other proxied connections, constituting a denial-of-service condition.", "risk_and_exploitability": "The severity indicated by the CVSS score of 4.3 reflects moderate risk, while the EPSS score of less than 1\u202f% suggests a low probability of exploitation in the wild. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires only network access to the Dovecot service and can be performed from a single IP address. By opening many connections and sending repeatedly constructed NOOP commands, an attacker can consume significant memory resources and trigger a crash, thereby lowering availability of the mail server."}}}}, "created": "2026-03-27T15:47:10.148345+00:00", "updated": "2026-03-30T07:02:13.352296+00:00", "vendors": ["open-xchange", "open-xchange$PRODUCT$ox_dovecot_pro"]}