Medium

Microsoft Exchange OWA link rewriting elevation of privilege

IdentifiersCVE-2018-0940CWE-601

CVE-2018-0940 is an elevation of privilege vulnerability in Microsoft Exchange Outlook Web Access (OWA) affecting Microsoft Exchange Server 2010 Service Pack 3 Update Rollup 20, Microsoft Exchange Server 2013 Cumulative Update 18 and 19, Microsoft Exchange Server 2013 Service Pack 1, and Microsoft Exchange Server 2016 Cumulative Update 7 and 8. The flaw is caused by the way OWA rewrites links contained in the body of an email message. Improper handling of rewritten links can allow an attacker to leverage crafted email content to obtain elevated privileges in the context of the targeted Exchange web application workflow.

For your environment

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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 can allow elevation of privilege within the affected Exchange OWA environment. An attacker may be able to act with greater permissions than intended in the webmail context, potentially enabling unauthorized access to data or actions available to a more privileged user or session.

Mitigation

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

If immediate patching is not possible, reduce exposure by limiting access to OWA to trusted networks or through controlled remote access paths, closely monitoring Exchange web access activity for anomalous behavior, and minimizing opportunities for users to interact with untrusted email content in OWA. These measures are only temporary and do not remove the underlying flaw.

Remediation

Patch, then assume compromise.

Apply the Microsoft security updates that address CVE-2018-0940 for the affected Exchange Server versions. Systems running the listed vulnerable builds should be upgraded to the corresponding fixed Exchange update level provided by Microsoft.

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

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

ACTIVITY FEED

Recent activity

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

2 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.

What this page doesn’t show

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This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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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