Medium

Microsoft Exchange Information Disclosure Vulnerability

IdentifiersCVE-2019-1084CWE-20

CVE-2019-1084 is an information disclosure vulnerability in Microsoft Exchange caused by improper handling of entity Display Names containing non-printable characters. An authenticated attacker can create Exchange entities with invalid display names that are not rendered visibly when those entities are added to conversations. This allows malicious or deceptive conversation participants to remain effectively hidden from users. The issue was addressed by adding validation of display names at creation time in Exchange and by ensuring invalid display names are rendered correctly in Microsoft Outlook clients.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an authenticated attacker to conceal the presence or identity of entities participating in Exchange conversations, resulting in information disclosure and conversation integrity issues. This can mislead users about who is included in a message thread or discussion, potentially exposing sensitive communications to hidden recipients or enabling deceptive collaboration scenarios. The available information does not indicate direct code execution or privilege escalation from this flaw alone.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, restrict the ability to create or modify Exchange entities to trusted administrators and tightly control authenticated access to Exchange administrative and provisioning functions. Monitor for anomalous or malformed directory objects and review conversation membership and recipient lists for inconsistencies. These measures may reduce exposure but do not fully remediate the underlying flaw.

Remediation

Patch, then assume compromise.

Apply the Microsoft security update released for Exchange that validates display names during entity creation and corrects client-side rendering behavior in Microsoft Outlook for invalid display names. Ensure both vulnerable Exchange server components and affected Outlook clients are updated where applicable so malformed display names cannot be used to hide conversation participants.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Microsoft CorporationExchange Serverapplication

Microsoft CorporationLyncapplication

Microsoft CorporationLync Basicapplication

Microsoft CorporationMail And Calendarapplication

Microsoft CorporationOfficeapplication

Microsoft CorporationOffice 365 Proplusapplication

Microsoft CorporationOutlookapplication

Microsoft CorporationSkype For Businessapplication

Microsoft CorporationSkype For Business Basicapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

3 SOURCESView more in app

msrc microsoftNews

Mar 2, 2021

CVE-2021-27065 - Security Update Guide - Microsoft - Microsoft Exchange Server Remote Code Execution Vulnerability

Specific vulnerability listed in the content with severity Important.

msrc microsoftNews

Mar 2, 2021

CVE-2021-26857 - Security Update Guide - Microsoft - Microsoft Exchange Server Remote Code Execution Vulnerability

Specific named vulnerability listed in the content; no product or technical description is provided beyond severity/date and tabular flags.

sonicwallNews

Jul 10, 2019

Microsoft Security Bulletin Coverage for July 2019

An information disclosure vulnerability in Microsoft Exchange.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity