# CVE-2026-21806: HCL BigFix Service Management was affected with Admin Session Concurrency vulnerability (CVE-2026-21806)

> Attackers can hijack administrative sessions due to lack of session concurrency limits, gaining full privileged access to HCL BigFix Service Management.

- **Severity:** Low 3.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N`)
- **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:** 18 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** GHSA-6qc5-jgrf-h9g7

## What is CVE-2026-21806?

CVE-2026-21806 is a low-severity authentication bypass vulnerability in HCL BigFix  Service Management, published on 18 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

HCL BigFix Service Management is affected by an Administrative Session Concurrency vulnerability. The application allows multiple simultaneous authenticated sessions for the same administrative account, which could enable an unauthorized attacker to predict or hijack valid session identifiers. Successful exploitation allows an attacker to compromise affected administrative sessions and execute actions with full privileged user permissions.

Weakness: CWE-557

## Which versions are affected by CVE-2026-21806?

It affects 1 product.


Products: Hcltech Bigfix Service Management.

## How do I fix CVE-2026-21806?

No fix has been published for CVE-2026-21806 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-21806 being exploited?

There is no known exploitation of CVE-2026-21806 in the wild and no public exploit code.

## Other vulnerabilities in HCL BigFix  Service Management

- [CVE-2026-67100](https://insights.sbomify.com/CVE-2026-67100/): HCL BigFix Service Management is affected by multiple security vulnerabilities. (critical 9.8)
- [CVE-2026-67101](https://insights.sbomify.com/CVE-2026-67101/): HCL BigFix Service Management is affected by multiple security vulnerabilities. (critical 9.3)
- [CVE-2024-30151](https://insights.sbomify.com/CVE-2024-30151/): HCL BigFix Service Management (SM) is susceptible to Broken Access Control Vulnerability (high 8.3)
- [CVE-2026-67102](https://insights.sbomify.com/CVE-2026-67102/): HCL BigFix Service Management is affected by multiple security vulnerabilities. (high 8.1)
- [CVE-2026-67103](https://insights.sbomify.com/CVE-2026-67103/): HCL BigFix Service Management is affected by multiple security vulnerabilities. (high 7.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21806 and fix it if it is affected.

What it is: CVE-2026-21806 is a low-severity authentication bypass vulnerability in HCL BigFix  Service Management, published on 18 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-21806 in the wild and no public exploit code.

Affected product: HCL BigFix  Service Management. 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-2026-21806/ (Markdown: https://insights.sbomify.com/CVE-2026-21806/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21806
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21806
- OSV: https://osv.dev/vulnerability/CVE-2026-21806

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21806/
Summaries are generated and may contain mistakes; the official description above is the record.