CVE-2026-43827: shiro Session Fixation — Fix

Description

Default configurations of Apache Shiro have a session fixation vulnerability. This issue affects Apache Shiro from 1.0 to 2.1.0, and 3.0.0-alpha-1. Users are recommended to upgrade to version 2.1.1, or 3.0.0-alpha-2 or later, which fixes the issue. In the affected versions, when a session already exists, it is not invalidated upon successful login, nor is a new session being generated with a new ID.

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CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0041

Probability of exploitation

0.33%

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-384 CWE-384

Affected Products

Vendor	Product	Versions
apache	shiro	< 2.1.1
apache	shiro	All

References

Advisories & Patches

https://shiro.apache.org/security-reports.html#cve_2026_43827

Other References

http://www.openwall.com/lists/oss-security/2026/05/25/6

Frequently Asked Questions

What is CVE-2026-43827? +

Default configurations of Apache Shiro have a session fixation vulnerability. This issue affects Apache Shiro from 1.0 to 2.1.0, and 3.0.0-alpha-1. Users are recommended to upgrade to version 2.1.1, or 3.0.0-alpha-2 or later, which fixes the issue. In the affected versions, when a session already exists, it is not invalidated upon successful login, nor is a new session being generated with a new ID. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-43827? +

CVE-2026-43827 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0041, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-43827? +

CVE-2026-43827 affects products from apache, specifically: shiro. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-43827? +

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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