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CVE-2026-27857 (GCVE-0-2026-27857)

Vulnerability from cvelistv5 – Published: 2026-03-27 08:10 – Updated: 2026-07-15 01:12
VLAI
Summary
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.
Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-27 12:39 UTC
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
URL Tags
https://documentation.open-xchange.com/dovecot/se… vendor-advisory
https://access.redhat.com/security/cve/CVE-2026-27857 vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2452179 issue-trackingx_refsource_REDHAT
https://security.access.redhat.com/data/csaf/v2/v… x_sadp-csaf-vex
https://access.redhat.com/errata/RHSA-2026:26564 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:17602 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:13498 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:19149 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:13830 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:19455 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:19453 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:18053 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:17630 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:17628 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:17625 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:17626 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:13857 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:19364 vendor-advisoryx_refsource_REDHAT
Impacted products
Vendor Product Version CPE status
Open-Xchange GmbH OX Dovecot Pro Affected: 0 , ≤ 2.3.0 (semver)
guessed Create a notification for this product.
Red Hat Red Hat Enterprise Linux 10 Unaffected: 1:2.3.21-16.el10_1.1 , < * (rpm)
Unaffected: 1:2.3.21-19.el10_2 , < * (rpm)
    cpe:/o:redhat:enterprise_linux:10.1
    cpe:/o:redhat:enterprise_linux:10.2
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support Unaffected: 1:2.3.21-16.el10_0.1 , < * (rpm)
    cpe:/o:redhat:enterprise_linux_eus:10.0
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support Unaffected: 1:2.2.36-8.el7_9.1 , < * (rpm)
    cpe:/o:redhat:rhel_els:7
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8 Unaffected: 1:2.3.16-7.el8_10 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:8
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support Unaffected: 1:2.3.8-9.el8_4.1 , < * (rpm)
    cpe:/a:redhat:rhel_aus:8.4
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On Unaffected: 1:2.3.8-9.el8_4.1 , < * (rpm)
    cpe:/a:redhat:rhel_eus_long_life:8.4
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support Unaffected: 1:2.3.16-2.el8_6.1 , < * (rpm)
    cpe:/a:redhat:rhel_aus:8.6
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service Unaffected: 1:2.3.16-2.el8_6.1 , < * (rpm)
    cpe:/a:redhat:rhel_tus:8.6
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions Unaffected: 1:2.3.16-2.el8_6.1 , < * (rpm)
    cpe:/a:redhat:rhel_e4s:8.6
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service Unaffected: 1:2.3.16-3.el8_8.1 , < * (rpm)
    cpe:/a:redhat:rhel_tus:8.8
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions Unaffected: 1:2.3.16-3.el8_8.1 , < * (rpm)
    cpe:/a:redhat:rhel_e4s:8.8
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 9 Unaffected: 1:2.3.16-15.el9_7.1 , < * (rpm)
Unaffected: 1:2.3.16-18.el9_8 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions Unaffected: 1:2.3.16-3.el9_0.1 , < * (rpm)
    cpe:/a:redhat:rhel_e4s:9.0
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions Unaffected: 1:2.3.16-8.el9_2.2 , < * (rpm)
    cpe:/a:redhat:rhel_e4s:9.2
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support Unaffected: 1:2.3.16-11.el9_4.2 , < * (rpm)
    cpe:/a:redhat:rhel_eus:9.4
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support Unaffected: 1:2.3.16-15.el9_6.1 , < * (rpm)
    cpe:/a:redhat:rhel_eus:9.6
Create a notification for this product.
Red Hat Red Hat Enterprise Linux 6     cpe:/o:redhat:enterprise_linux:6
Create a notification for this product.
Show details on NVD website
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            "value": "RHSA-2026:19453: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream E4S (v.8.6), Red Hat Enterprise Linux AppStream TUS (v.8.6)"
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            "value": "RHSA-2026:18053: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8)"
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            "lang": "en",
            "value": "RHSA-2026:17630: Red Hat Enterprise Linux AppStream E4S (v.9.0)"
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            "value": "RHSA-2026:17628: Red Hat Enterprise Linux AppStream E4S (v.9.2)"
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            "value": "RHSA-2026:17625: Red Hat CodeReady Linux Builder EUS (v.9.4), Red Hat Enterprise Linux AppStream EUS (v.9.4)"
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            "lang": "en",
            "value": "RHSA-2026:17626: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6)"
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            "lang": "en",
            "value": "RHSA-2026:13857: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)"
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            "lang": "en",
            "value": "RHSA-2026:19364: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)"
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            "lang": "en",
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            "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."
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    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-27857\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-03-27T12:39:00.311649Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-03-27T12:39:41.889Z\"}}], \"cna\": {\"source\": {\"defect\": \"DOV-8816\", \"discovery\": \"EXTERNAL\"}, \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 4.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"LOW\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Open-Xchange GmbH\", \"modules\": [\"core\"], \"product\": \"OX Dovecot Pro\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"2.3.0\"}], \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json\", \"tags\": [\"vendor-advisory\"]}], \"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.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"cwe\", \"cweId\": \"CWE-400\", \"description\": \"Uncontrolled Resource Consumption\"}]}], \"providerMetadata\": {\"orgId\": \"8ce71d90-2354-404b-a86e-bec2cc4e6981\", \"shortName\": \"OX\", \"dateUpdated\": \"2026-03-27T12:33:29.627Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-27857\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-03-27T12:39:48.150Z\", \"dateReserved\": \"2026-02-24T08:46:09.373Z\", \"assignerOrgId\": \"8ce71d90-2354-404b-a86e-bec2cc4e6981\", \"datePublished\": \"2026-03-27T08:10:20.761Z\", \"assignerShortName\": \"OX\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.