CVE-2020-9488Network attack vector

Log disclosure via missing TLS hostname validation

Published Apr 27, 2020 · Updated May 29, 2026

Improper certificate validation in affected Apache Log4j releases allows man-in-the-middle attackers to read logs sent over TLS. The SslConfiguration path accepts a peer certificate whose host name does not match the requested SMTP, HTTP, Socket, or Syslog destination. The flaw requires an affected appender configuration and interception of its outbound TLS traffic; system-property SSL configurations are not affected.

CVSS severity3.7
Low
EPSS probability8.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in affected Apache Log4j releases allows man-in-the-middle attackers to read logs sent over TLS. The SslConfiguration path accepts a peer certificate whose host name does not match the requested SMTP, HTTP, Socket, or Syslog destination. The flaw requires an affected appender configuration and interception of its outbound TLS traffic; system-property SSL configurations are not affected.

The record

CVE
CVE-2020-9488
Published
Apr 27, 2020
Updated
May 29, 2026
Vendor
The Apache Software Foundation
Product
Apache Log4j
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 27, 2020CVE publishedPublication date reported by the CVE source.
  2. May 29, 2026Record 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=log4j-core <2.12.3
  2. Affected versionversion=log4j-core 2.13.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Log4jversion=log4j-core <2.12.3; version=log4j-core 2.13.0

Published CVSS scores

3.7NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
3.7CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
3.7Apache Logging ServicesCVSS:3.1/AV:N/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 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-295Improper Certificate Validation
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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