# CVE-2017-18106: Auth bypass in Crowd

> Remote attackers can hijack user sessions by exploiting identifier hash collisions in Atlassian Crowd, leading to unauthorized access.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Mar 2019
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-4vj3-9qjv-52hq

## What is CVE-2017-18106?

CVE-2017-18106 is a high-severity authentication bypass vulnerability in Atlassian Crowd, published on 29 Mar 2019. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The identifier_hash for a session token in Atlassian Crowd before version 2.9.1 could potentially collide with an identifier_hash for another user or a user in a different directory, this allows remote attackers who can authenticate to Crowd or an application using Crowd for authentication to gain access to another user's session provided they can make their identifier hash collide with another user's session identifier hash.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2017-18106?

It affects 1 product.


Products: Atlassian Crowd.

## How do I fix CVE-2017-18106?

No fix has been published for CVE-2017-18106 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-18106 being exploited?

There is no known exploitation of CVE-2017-18106 in the wild and no public exploit code.

## Other vulnerabilities in Atlassian Crowd

- [CVE-2019-11580](https://insights.sbomify.com/CVE-2019-11580/): Atlassian Crowd and Crowd Data Center Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-43782](https://insights.sbomify.com/CVE-2022-43782/): Auth bypass in Crowd Data Center (critical 9.8)
- [CVE-2016-6496](https://insights.sbomify.com/CVE-2016-6496/): Deserialization in n/a (critical 9.8)
- [CVE-2017-18105](https://insights.sbomify.com/CVE-2017-18105/): Auth bypass in Crowd (high 8.1)
- [CVE-2018-20238](https://insights.sbomify.com/CVE-2018-20238/): Auth bypass in Crowd (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-18106 and fix it if it is affected.

What it is: CVE-2017-18106 is a high-severity authentication bypass vulnerability in Atlassian Crowd, published on 29 Mar 2019. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2017-18106 in the wild and no public exploit code.

Affected product: Atlassian Crowd. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2017-18106/ (Markdown: https://insights.sbomify.com/CVE-2017-18106/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-18106
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-18106
- OSV: https://osv.dev/vulnerability/CVE-2017-18106

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-18106/
Summaries are generated and may contain mistakes; the official description above is the record.