CVE-2026-40542

Description

Missing critical step in authentication in Apache HttpClient 5.6 allows an attacker to cause the client to accept SCRAM-SHA-256 authentication without proper mutual authentication verification. Users are recommended to upgrade to version 5.6.1, which fixes this issue.

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CVSS v3.1 Score

7.3

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

EPSS — Exploit Prediction

0.0010

Probability of exploitation

0.27%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-304 CWE-304

Affected Products

Vendor	Product	Versions
apache	httpclient	All

References

Advisories & Patches

https://lists.apache.org/thread/tfmgv86xr0z1y096vs3z0y315t1v3o97

Other References

http://www.openwall.com/lists/oss-security/2026/04/22/5

Frequently Asked Questions

What is CVE-2026-40542? +

Missing critical step in authentication in Apache HttpClient 5.6 allows an attacker to cause the client to accept SCRAM-SHA-256 authentication without proper mutual authentication verification. Users are recommended to upgrade to version 5.6.1, which fixes this issue. It has a CVSS v3.1 base score of 7.3 (HIGH).

How severe is CVE-2026-40542? +

CVE-2026-40542 has a CVSS v3.1 score of 7.3 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0010, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40542? +

CVE-2026-40542 affects products from apache, specifically: httpclient. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40542? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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