CVE-2020-26082Network attack vector

Email filter bypass via password-protected ZIP handling

Published Aug 4, 2023 · Updated Jul 9, 2025

Improper input validation in Cisco Secure Email before 13.5.2 allows remote attackers to bypass content filters with crafted ZIP files. The ZIP decompression engine mishandles password-protected archives, so a malicious inner file is not subjected to the configured filtering decision. Exploitation requires only delivery of the crafted archive to an affected appliance, and the resulting email reaches recipients despite a filter that should drop it.

CVSS severity5.8
Medium
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Cisco Secure Email before 13.5.2 allows remote attackers to bypass content filters with crafted ZIP files. The ZIP decompression engine mishandles password-protected archives, so a malicious inner file is not subjected to the configured filtering decision. Exploitation requires only delivery of the crafted archive to an affected appliance, and the resulting email reaches recipients despite a filter that should drop it.

The record

CVE
CVE-2020-26082
Published
Aug 4, 2023
Updated
Jul 9, 2025
Vendor
ClamAV
Product
Cisco Secure Email
Classifications
CWE-20, T1027.013
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 4, 2023CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 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=N/A

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Secure Emailversion=N/A

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.8Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1027.013Encrypted/Encoded File

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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