# CVE-2026-43827: Apache Shiro: Session fixation: new session is not created after login by default

> Attackers can hijack user sessions because Apache Shiro does not regenerate session IDs after login by default, allowing session fixation attacks.

- **Severity:** Medium 5.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:L/SI:N/SA:N/AU:Y/R:U/RE:L/U:Amber`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 May 2026
- **Updated:** 26 May 2026
- **Also known as:** CLEANSTART-2026-YW87633, DEBIAN-CVE-2026-43827, ECHO-46dc-0019-0617, GHSA-fcvm-3cpj-f9qx, MINI-324g-j2h7-g92f, MINI-3456-qm86-wgrf, MINI-37rw-2v57-84q5, MINI-3899-g9g2-876p, MINI-3h84-4hgv-3f4p, MINI-3xj3-xc2g-gg63, MINI-56j8-2fwp-g9jq, MINI-5rpm-fxf7-vmrp, MINI-5w77-f2gg-97qr, MINI-7ph9-58mq-843q, MINI-7vqm-2rqr-48r9, MINI-83qw-pmf3-f3j2, MINI-97hm-x394-pr5h, MINI-9gj4-fp3f-7q39, MINI-cg87-pv48-3q66, MINI-f8jj-6393-mcvg, MINI-ffrw-j969-49mr, MINI-grwv-6fcp-8wmr, MINI-jpqr-rrxv-vcg3, MINI-pjf6-4xmg-6wqr, MINI-rjxf-465h-67q9, MINI-v6c5-xc8m-67fj, MINI-x3jj-x46q-g7gf, UBUNTU-CVE-2026-43827

## What is CVE-2026-43827?

CVE-2026-43827 is a medium-severity authentication bypass vulnerability in Apache Shiro, published on 25 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-384 (Session Fixation)

## Which versions are affected by CVE-2026-43827?

4 open source packages ship an affected version, including org.apache.shiro:shiro-core. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.shiro:shiro-core` | Maven | From 1.0.0-incubating | 2.2.0 |
| `org.apache.shiro:shiro-core` | Maven | From 1.0.0-incubating | 2.2.0 |
| `org.apache.shiro:shiro-core` | Maven | From 3.0.0-alpha-1 | 3.0.0-alpha-2 |
| `org.apache.shiro:shiro-core` | Maven | From 3.0.0-alpha-1 | 3.0.0-alpha-2 |

Products: Apache Shiro.

## How do I fix CVE-2026-43827?

Upgrade org.apache.shiro:shiro-core to a fixed version for your release line: 2.2.0 or 3.0.0-alpha-2.

## Is CVE-2026-43827 being exploited?

There is no known exploitation of CVE-2026-43827 in the wild and no public exploit code.

## Other vulnerabilities in Apache Shiro

- [CVE-2023-34478](https://insights.sbomify.com/CVE-2023-34478/): Path Traversal in Apache Shiro (critical 9.8)
- [CVE-2022-40664](https://insights.sbomify.com/CVE-2022-40664/): Authentication Bypass Vulnerability in Shiro when forwarding or including via RequestDispatcher (critical 9.8)
- [CVE-2022-32532](https://insights.sbomify.com/CVE-2022-32532/): Authentication Bypass Vulnerability (critical 9.8)
- [CVE-2021-41303](https://insights.sbomify.com/CVE-2021-41303/): Apache Shiro vulnerable to a specially crafted HTTP request causing an authentication bypass (critical 9.8)
- [CVE-2020-17523](https://insights.sbomify.com/CVE-2020-17523/): Authentication bypass in Apache Shiro (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43827 and fix it if it is affected.

What it is: CVE-2026-43827 is a medium-severity authentication bypass vulnerability in Apache Shiro, published on 25 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-43827 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.shiro:shiro-core (Maven): affected from 1.0.0-incubating; fixed in 2.2.0
- org.apache.shiro:shiro-core (Maven): affected from 1.0.0-incubating; fixed in 2.2.0
- org.apache.shiro:shiro-core (Maven): affected from 3.0.0-alpha-1; fixed in 3.0.0-alpha-2
- org.apache.shiro:shiro-core (Maven): affected from 3.0.0-alpha-1; fixed in 3.0.0-alpha-2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43827/ (Markdown: https://insights.sbomify.com/CVE-2026-43827/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43827
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43827
- OSV: https://osv.dev/vulnerability/CVE-2026-43827

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43827/
Summaries are generated and may contain mistakes; the official description above is the record.