CVE-2024-49040Network attack vector

Sender spoofing via malformed P2 FROM headers

Published Nov 12, 2024 · Updated Jul 8, 2025

Spoofing in Microsoft Exchange Server 2016 CU23 and 2019 CU13 and CU14 allows remote attackers to impersonate trusted email senders. Transport-layer P2 FROM verification accepts some non-RFC 5322 headers and passes them to email clients, which display the forged sender as legitimate. Unauthenticated inbound mail delivery is sufficient, and the resulting identity misrepresentation can make phishing messages appear trustworthy.

CVSS severityUnavailable
Unscored
EPSS probability7.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Spoofing in Microsoft Exchange Server 2016 CU23 and 2019 CU13 and CU14 allows remote attackers to impersonate trusted email senders. Transport-layer P2 FROM verification accepts some non-RFC 5322 headers and passes them to email clients, which display the forged sender as legitimate. Unauthenticated inbound mail delivery is sufficient, and the resulting identity misrepresentation can make phishing messages appear trustworthy.

The record

CVE
CVE-2024-49040
Published
Nov 12, 2024
Updated
Jul 8, 2025
Vendor
Microsoft
Product
Microsoft Exchange Server 2019 Cumulative Update 14
Classifications
CWE-451, T1036
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 2024CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.02.0 <15.02.1544.014

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Exchange Server 2019 Cumulative Update 14version=15.02.0 <15.02.1544.014
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 13version=15.02.0 <15.02.1258.039
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 23version=15.01.0 <15.01.2507.044

Published CVSS scores

7.5MicrosoftCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-451User Interface (UI) Misrepresentation of Critical Information
T1036Masquerading

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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