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CVE Record

CVE-2026-27858: Attacker can send a specifically crafted message before authentication that causes managesieve to allocate...

Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. 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

CVE-2026-27858 is a denial-of-service issue in OX Dovecot Pro’s ManageSieve login handling. An unauthenticated attacker can send a specially crafted pre-login message that triggers excessive memory allocation and repeated process crashes, making ManageSieve unavailable.

Executive priority

Treat this as a high-priority availability risk for mail infrastructure where ManageSieve is exposed. Patch or restrict access promptly, with urgency highest for internet-reachable deployments.

Technical view

The flaw is classified as CWE-400/CWE-770 resource exhaustion. CVSS 3.1 is 7.5, with network access, low attack complexity, no privileges, no user interaction, and high availability impact. The supplied data names OX Dovecot Pro and ManageSieve, but affected version detail is incomplete.

Likely exposure

Exposure is most likely where ManageSieve is enabled and reachable over the network, especially from untrusted networks. Environments using vendor or Red Hat Dovecot-related packages should verify advisory applicability.

Exploitation context

The source bundle says no publicly available exploits are known, and KEV is false. However, the attack is unauthenticated and network-accessible, so exposed ManageSieve services could still face availability risk.

Researcher notes

The strongest evidence supports pre-authentication resource exhaustion in managesieve-login. The supplied affected-version data is sparse, so product/version conclusions should be validated against the Open-Xchange CSAF, Red Hat VEX, and relevant errata.

Mitigation direction

  • Install the fixed version identified by Open-Xchange or Red Hat guidance.
  • Restrict ManageSieve access to trusted networks or authenticated administrative paths.
  • Disable ManageSieve if the service is not required.
  • Review applicable Red Hat errata for affected package updates.
  • Monitor memory pressure and managesieve-login crash patterns.

Validation and detection

  • Inventory Dovecot/OX Dovecot Pro deployments and ManageSieve usage.
  • Confirm whether ManageSieve is reachable from untrusted networks.
  • Compare installed packages against vendor CSAF and Red Hat advisories.
  • Check logs for repeated managesieve-login crashes or abnormal memory allocation.
  • Document compensating network controls where patching is delayed.
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.

Open ATT&CK lookup
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-2026-27858 mapping review

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

Open ATT&CK lookup
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: yesTechnical 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:H3.93.6OX
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

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-27858Attack 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 crafted message before authentication
other:Red Hat severity ratingcvssV3_1
  • 2026-03-27T09:01:45.192Z: Reported to Red Hat.
  • 2026-03-27T08:10:21.424Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Open-Xchange GmbHOX Dovecot Pro0, 0, 0unaffected
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