CVE-2026-4942

Received Received - Intake

IBM i TLS Downgrade Vulnerability

Publication date: 2026-07-17

Last updated on: 2026-07-17

Assigner: IBM Corporation

Description

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to send a specifically crafted message and downgrade the Transport Layer Security (TLS) protocol to a version disabled in the server configuration.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-07-17

Last Modified

2026-07-17

Generated

2026-07-18

AI Q&A

2026-07-18

EPSS Evaluated

N/A

NVD

CVE-2026-4942

EUVD

EUVD-2026-45292

Affected Vendors & Products

Vendor	Product	Version / Range
ibm	i	7.6
ibm	i	7.5
ibm	i	7.4
ibm	i	7.3
ibm	ibm_i	to 7.4 (exc)
ibm	ibm_i	to 7.5 (exc)
ibm	ibm_i	to 7.6 (exc)
ibm	ibm_i	7.6

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-757	A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest algorithm that is available to both parties.

Attack-Flow Graph

Executive Summary

IBM i 7.6, 7.5, 7.4, and 7.3 are vulnerable to a TLS algorithm downgrade attack. A remote attacker can send a specially crafted message to force the server to use a less-secure TLS version that was disabled in its configuration.

Detection Guidance

To detect this vulnerability, check if your IBM i system is running affected versions (7.3, 7.4, 7.5, 7.6) and verify if TLS downgrade attacks are possible. Use IBM i commands like DSPPTF to check installed PTFs and NETSTAT to review active TLS connections. Monitor network traffic for unexpected TLS version downgrades.

Impact Analysis

This vulnerability allows an attacker to downgrade TLS to a weaker version, potentially exposing sensitive data transmitted over the network to interception or decryption. Systems using affected IBM i versions could be at risk of data breaches or unauthorized access.

Compliance Impact

Using a weaker TLS version may violate compliance requirements for secure data transmission in standards like GDPR and HIPAA, which mandate strong encryption for protecting sensitive data. This could lead to non-compliance and potential legal or financial penalties.

Mitigation Strategies

Apply the provided IBM PTFs (MJ09138 for 7.3, MJ09139 for 7.4, MJ09140 for 7.5, MJ09141 for 7.6) to patch the vulnerability. If running unsupported versions, upgrade to a supported release. Ensure TLS configurations are set to reject downgrade attempts and monitor for unusual TLS activity.

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