CVE-2021-25376

Plaintext message disclosure via failed STARTTLS negotiation

Published Apr 9, 2021 · Updated Aug 3, 2024

Information exposure in Samsung Email before 6.1.41.0 allows man-in-the-middle attackers to read mailbox messages after failed STARTTLS negotiation. Improper synchronization logic continues mailbox message transfer in plaintext rather than preserving transport encryption when STARTTLS negotiation fails. Exploitation requires an attacker able to interfere with the mail connection, and the consequence is limited to disclosure of affected mailbox messages.

CVSS severity5.3
Medium
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information exposure in Samsung Email before 6.1.41.0 allows man-in-the-middle attackers to read mailbox messages after failed STARTTLS negotiation. Improper synchronization logic continues mailbox message transfer in plaintext rather than preserving transport encryption when STARTTLS negotiation fails. Exploitation requires an attacker able to interfere with the mail connection, and the consequence is limited to disclosure of affected mailbox messages.

The record

CVE
CVE-2021-25376
Published
Apr 9, 2021
Updated
Aug 3, 2024
Vendor
Samsung Electronics Co., Ltd.
Product
Samsung Email
Classifications
CWE-662, CWE-200, T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=unspecified <6.1.41.0

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Samsung Electronics Co., Ltd. · Samsung Emailversion=unspecified <6.1.41.0

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1Samsung MobileCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-662Improper Synchronization
CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1557Adversary-in-the-Middle

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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