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CVE Record

CVE-2026-27857: Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage.

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.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a denial-of-service flaw in OX Dovecot Pro. A remote unauthenticated client can cause extra memory allocation with a crafted NOOP command and hold memory by leaving the command unfinished. Many connections could exhaust memory limits and kill the process, disrupting proxied mail connections.

Executive priority

High priority for organizations running exposed Dovecot mail proxy infrastructure. The business risk is service outage, not data theft, but a remote unauthenticated availability flaw can still disrupt email operations at scale.

Technical view

CVE-2026-27857 is a resource consumption issue mapped to CWE-400 and CWE-770. The supplied CVSS vector is network, low complexity, no privileges, no user interaction, with high availability impact only. The bundle says longer commands disconnect clients, but unfinished commands can leave memory allocated for extended periods.

Likely exposure

Exposure is most relevant for internet-reachable OX Dovecot Pro deployments or Red Hat-distributed affected packages referenced by the advisories. The bundle does not provide complete affected version numbers beyond the OX Dovecot Pro entry, so inventory must be checked against vendor advisories.

Exploitation context

The source bundle says no publicly available exploits are known, and KEV is false. However, the condition is remotely reachable and unauthenticated, so exposed mail proxy services should treat this as an availability risk even without confirmed active exploitation.

Researcher notes

Evidence supports availability-only impact and resource exhaustion. The provided bundle names fixed-version installation but not precise fixed builds. Avoid assuming exploit availability or broader product impact beyond OX Dovecot Pro and the cited Red Hat advisory ecosystem.

Mitigation direction

  • Install the vendor fixed version; the bundle states there is no other remediation.
  • Check Open-Xchange and Red Hat advisories for exact package and version guidance.
  • Prioritize internet-facing mail proxy systems before internal-only deployments.
  • Monitor vendor updates if package applicability is unclear.

Validation and detection

  • Inventory OX Dovecot Pro and Red Hat-provided Dovecot-related packages.
  • Compare installed package versions against Open-Xchange and Red Hat advisory status.
  • Review mail proxy logs for unusual connection volume and incomplete commands.
  • Monitor process memory, VSZ limits, restarts, and dropped proxied connections.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-400: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-770: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-27857 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
19Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP
4.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L2.81.4OX

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-27857Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPdovecot: denial of service via specially crafted NOOP command
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T09:01:59.374Z: Reported to Red Hat.
  • 2026-03-27T08:10:20.761Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Open-Xchange GmbHOX Dovecot Pro0unaffected
Weakness

CWE details

CWE-400CWE-770

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-770 · source CWE mapping

Allocation of Resources Without Limits or Throttling

Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs