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CVE Record

CVE-2021-36093: DoS attack using PostMaster filters

It's possible to create an email which can be stuck while being processed by PostMaster filters, causing DoS. This issue affects: OTRS AG ((OTRS)) Community Edition 6.0.x version 6.0.1 and later versions. OTRS AG OTRS 7.0.x version 7.0.28 and prior versions; 8.0.x version 8.0.15 and prior versions.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-36093 lets a specially crafted email get stuck during OTRS PostMaster filter processing. The business impact is service disruption: ticket intake or mail processing may slow or stop, affecting support operations. The public source rates it medium severity, focused on availability rather than data theft.

Executive priority

Treat this as a moderate operational risk. It is not described as data compromise, but it can interrupt customer support or service desk workflows if exposed mail processing is affected.

Technical view

The issue is a network-reachable, unauthenticated denial-of-service condition in OTRS PostMaster filters, associated with CWE-185. Affected products include ((OTRS)) Community Edition 6.0.x from 6.0.1, OTRS 7.0.x through 7.0.28, and OTRS 8.0.x through 8.0.15.

Likely exposure

Exposure is likely where affected OTRS versions process inbound email from untrusted senders through PostMaster filters. Systems without external mail intake have reduced practical exposure.

Exploitation context

The CVE source states attack complexity is low and no authentication or user interaction is required. No KEV listing or supplied source confirms active exploitation.

Researcher notes

Evidence is limited to CVE metadata and the OTRS advisory reference. The CVSS vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L, so validation should focus on affected versions, mail intake exposure, and availability symptoms, not confidentiality impact.

Mitigation direction

  • Identify all OTRS and ((OTRS)) Community Edition deployments and versions.
  • Review the OTRS 2021-16 advisory for vendor-provided fixed versions or workarounds.
  • Prioritize remediation on internet-facing or high-volume mail intake systems.
  • Monitor inbound mail queues for stuck messages or unusual backlog growth.
  • Use vendor guidance before changing PostMaster filters in production.

Validation and detection

  • Confirm whether any deployment runs the affected version ranges.
  • Check whether PostMaster filters process untrusted inbound email.
  • Review mail-processing health metrics for persistent queue buildup.
  • Review OTRS logs for repeated PostMaster processing failures.
  • Verify remediation against vendor advisory guidance after changes.
Prepared
Confidence
medium
Sources
3

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

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cwe · low confidence lookup

CWE-185: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-36093 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (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:L

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.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

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
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.3Medium
CVSS 3.1 vector shape for CVE-2021-36093Attack 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:L

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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
OTRS AG((OTRS)) Community Edition6.0.1Listed
OTRS AGOTRS7.0.x, 8.0.xListed
Weakness

CWE details

CWE-185

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

CWE-185 · source CWE mapping

Incorrect Regular Expression

Incorrect Regular Expression represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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