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CVE-2026-40542 Apache Software Foundation CVE debrief

CVE-2026-40542 is a high-severity vulnerability in Apache HttpClient 5.6 that allows an attacker to bypass proper mutual authentication verification for SCRAM-SHA-256 authentication. This vulnerability was published on April 22, 2026, and modified on June 30, 2026. The CVSS score for this vulnerability is 7.3, indicating a high severity. Users are recommended to upgrade to version 5.6.1, which fixes this issue. The vulnerability is caused by a missing critical step in authentication, allowing an attacker to cause the client to accept SCRAM-SHA-256 authentication without proper verification.

Vendor
Apache Software Foundation
Product
Apache HttpClient
CVSS
HIGH 7.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-22
Original CVE updated
2026-09-09
Advisory published
2026-04-22
Advisory updated
2026-09-09

Who should care

Organizations using Apache HttpClient 5.6 should prioritize upgrading to version 5.6.1 to mitigate this vulnerability. This vulnerability could allow an attacker to bypass authentication, potentially leading to unauthorized access or data breaches. Security teams and developers responsible for maintaining and updating software dependencies should be aware of this issue and take necessary actions.

Technical summary

The vulnerability in Apache HttpClient 5.6 is due to a missing critical step in authentication, specifically for SCRAM-SHA-256 authentication. This allows an attacker to cause the client to accept this authentication method without proper mutual authentication verification. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L, indicating a high severity. The CWE for this vulnerability is CWE-304, related to Missing Critical Step in Authentication. Red Hat has also provided additional information and potential mitigations for this vulnerability.

Defensive priority

High priority should be given to upgrading Apache HttpClient to version 5.6.1. Security teams should also review and update their inventory of affected systems and monitor for potential exploitation attempts.

Recommended defensive actions

  • Upgrade Apache HttpClient to version 5.6.1
  • Review and update inventory of affected systems
  • Monitor for potential exploitation attempts
  • Implement additional authentication verification for SCRAM-SHA-256
  • Consider compensating controls for authentication

Evidence notes

The CVE record and NVD detail provide official information about the vulnerability. The source item URL provides additional metadata and references related to the vulnerability. Apache and Red Hat have provided information and potential mitigations for this vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-40542 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-40542

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-40542 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-40542

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Mitigation or vendor reference

    Unverified legacy reference

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

    [email protected] - Mailing List, Vendor Advisory

  • Source reference

    Unverified legacy reference

    URL: https://access.redhat.com/security/cve/CVE-2026-40542

    0b0ca135-0b70-47e7-9f44-1890c2a1c46c

  • Source reference

    Unverified legacy reference

    URL: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40542.json

    0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.