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CVE-2026-43827 Apache Software Foundation CVE debrief

Apache Shiro versions 1.0 through 2.1.0 and 3.0.0-alpha-1 contain a session fixation vulnerability in default configurations. When a session already exists, it is not invalidated upon successful login, and no new session with a fresh ID is generated. This allows an attacker who obtains a pre-authentication session ID to potentially hijack the authenticated session. The vulnerability was published on 2026-05-25 and last modified on 2026-05-26. Apache has released fixes in version 2.1.1 and 3.0.0-alpha-2 or later.

Vendor
Apache Software Foundation
Product
Apache Shiro
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-25
Original CVE updated
2026-07-24
Advisory published
2026-05-25
Advisory updated
2026-07-24

Who should care

Organizations running Apache Shiro-based applications with default session configurations, particularly those handling sensitive authentication flows. Security teams should prioritize patching if Shiro manages session state for authenticated users.

Technical summary

The vulnerability stems from Apache Shiro's default session management behavior where existing sessions are not invalidated and new session IDs are not generated upon successful authentication. This is classified as CWE-384 (Session Fixation). Affected versions include the entire 1.x through 2.1.0 release line and the 3.0.0-alpha-1 pre-release. The fix ensures proper session invalidation and ID regeneration on login.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Apache Shiro to version 2.1.1 or 3.0.0-alpha-2 or later
  • If immediate upgrade is not possible, review custom session management configurations for session invalidation on login
  • Audit applications for custom session handling that may override default Shiro behavior
  • Monitor for suspicious session activity involving pre-authentication session IDs

Evidence notes

The CVE description and Apache security reports confirm the session fixation behavior affects default configurations. CVSS 4.0 vector indicates network attack vector with low attack complexity, requiring user interaction.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-43827 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-43827

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

  • CVE-2026-43827 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-43827

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

Supplemental references

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.