Apache HttpClient: Missing Critical Step in Authentication
CVE-2026-40542 is a high-severity missing critical step in authentication vulnerability in Apache HttpClient from Apache, with a CVSS 3.1 base score of 7.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 5.6.1 as the first without the flaw, so updating Apache HttpClient to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.54% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Apache HttpClient to 5.6.1 or a later version.
- Read the advisory on lists.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 24 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.3 | High | CISA (ADP) |
| CVSS 3.1 | 7.3 | High | CNA |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Missing Critical Step in Authentication
The product implements an authentication technique, but it skips a step that weakens the technique.
More Missing Critical Step in Authentication vulnerabilities (CWE-304)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- openwall.com/lists/oss-security/2026/04/22/5Mailing List, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:60239
- access.redhat.com/errata/RHSA-2026:60246
- access.redhat.com/errata/RHSA-2026:60247
- access.redhat.com/errata/RHSA-2026:60248
- access.redhat.com/errata/RHSA-2026:60249
- access.redhat.com/errata/RHSA-2026:60250
- access.redhat.com/errata/RHSA-2026:60251
- access.redhat.com/errata/RHSA-2026:60252
- access.redhat.com/errata/RHSA-2026:60254
- access.redhat.com/errata/RHSA-2026:60256
- access.redhat.com/errata/RHSA-2026:60259
- access.redhat.com/security/cve/CVE-2026-40542
- bugzilla.redhat.com/show_bug.cgi?id=2460518
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40542.json
Recent Missing Critical Step in Authentication vulnerabilities
- 9.8 Critical severity
- 7.2 High severity
- 8.1 High severity
- 9.8 Critical severity
- 8.0 High severity
- 7.8 High severity
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