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CVE Record

CVE-2026-43964: Postfix before 3.8.16, 3.9 before 3.9.10, and 3.10 before 3.10.9 sometimes allows a buffer over-read and pr...

Postfix before 3.8.16, 3.9 before 3.9.10, and 3.10 before 3.10.9 sometimes allows a buffer over-read and process crash via an enhanced status code that lacks text after the third number.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A remote, unauthenticated party may be able to crash vulnerable Postfix processes by supplying a malformed mail status code. The documented impact is service disruption, not data theft or message alteration. Internet-facing mail infrastructure warrants prompt attention because exploitation requires neither credentials nor user interaction.

Executive priority

Treat this as a high-priority availability issue for exposed mail infrastructure. Schedule expedited patching, particularly where email disruption would affect customer communications, authentication, alerts, or business operations. Emergency incident posture is not justified solely by this bundle because active exploitation is not documented.

Technical view

Postfix can perform a buffer over-read when an enhanced status code contains three numeric components but no following text. Affected releases are those before 3.8.16, 3.9 releases before 3.9.10, and 3.10 releases before 3.10.9. CVSS 3.1 is 7.5, reflecting network-accessible, low-complexity denial of service without confidentiality or integrity impact.

Likely exposure

Potential exposure exists wherever a vulnerable Postfix installation processes attacker-controlled enhanced status codes. Publicly reachable mail systems are the clearest concern. The supplied evidence does not identify specific configurations, operating modes, or components that eliminate or increase exposure, so organizations should confirm installed packages and vendor applicability.

Exploitation context

The CVSS vector indicates remote, unauthenticated, low-complexity exploitation requiring no user action. The supplied bundle marks this CVE as absent from KEV and provides no evidence of active exploitation, public exploit availability, or attacks in the wild. Process crashes may interrupt mail handling, but operational consequences depend on supervision and restart behavior.

Researcher notes

The flaw is categorized as CWE-193 and manifests as a buffer over-read followed by process termination when status text is absent after the third numeric component. Available evidence supports denial of service only. It does not establish memory disclosure, code execution, exploit reliability, affected execution paths, or configuration-specific reachability.

Mitigation direction

  • Upgrade relevant branches to Postfix 3.8.16, 3.9.10, 3.10.9, or later.
  • For vendor-packaged Postfix, apply the applicable distribution security update or Red Hat erratum.
  • Prioritize publicly reachable mail systems and high-availability mail gateways.
  • Monitor Postfix crashes and abnormal restarts until remediation is complete.

Validation and detection

  • Inventory Postfix versions across mail servers, gateways, containers, and appliance-managed installations.
  • Compare installed versions with the fixed threshold for each relevant branch.
  • Confirm the applicable vendor package or Red Hat erratum is installed.
  • Verify services restarted successfully and report the corrected package version.
  • Review crash and restart logs for suspicious recurrence; logs alone cannot establish exploitation.
Prepared
Confidence
high
Sources
12

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-193: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-43964 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
3ADP providers
13Source 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
3.7CVSS 3.1LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L2.21.4mitre

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-43964Attack 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
CVECVE Program Container
redhat-SADPpostfix: buffer over-read via malformed enhanced status code
other:Red Hat severity ratingcvssV3_1
  • 2026-05-04T19:01:26.972Z: Reported to Red Hat.
  • 2026-05-04T18:10:10.509Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
PostfixPostfix2.3, 3.9, 3.10unaffected
Weakness

CWE details

CWE-193

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

CWE-193 · source CWE mapping

Off-by-one Error

Off-by-one Error represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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