# CVE-2026-76258: Use of Hard-coded Cryptographic Key through Companion App Registration in Splunk Secure Gateway

> A hard-coded key allows non-admin users to register malicious companion apps, redirecting mobile user tokens to attacker-controlled URLs and compromising data.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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:** 19 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** GHSA-3mh4-7c3j-c9mg

## What is CVE-2026-76258?

CVE-2026-76258 is a medium-severity vulnerability in Splunk Splunk, published on 19 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In Splunk Enterprise versions below 10.4.2, 10.2.6, 10.0.9, and 9.4.14, and Splunk Secure Gateway versions below 3.10.10, 3.9.24, and 3.8.71, a user who does not hold the "admin" or "power" Splunk roles could register an arbitrary companion app and cause Splunk Secure Gateway to forward mobile user requests, including tokens that compromise all relevant data available to the affected mobile user, to an attacker-controlled Uniform Resource Locator (URL). The vulnerability is possible because a hard-coded cryptographic key in the Splunk Secure Gateway companion app registration handler allows for arbitrary callback URL registration without restriction. For more information see Define roles on the Splunk platform with capabilities (https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/10.2/manage-splunk-platform-users-and-roles/define-roles-on-the-splunk-platform-with-capabilities) in the Splunk documentation.

Weakness: CWE-321 (Use of Hard-coded Cryptographic Key)

## Which versions are affected by CVE-2026-76258?

It affects 2 products.


Products: Splunk Splunk, Splunk Splunk Secure Gateway.

## How do I fix CVE-2026-76258?

No fix has been published for CVE-2026-76258 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-76258 being exploited?

There is no known exploitation of CVE-2026-76258 in the wild and no public exploit code.

## Other vulnerabilities in Splunk Splunk

- [CVE-2026-20253](https://insights.sbomify.com/CVE-2026-20253/): Splunk Enterprise Missing Authentication for Critical Function (critical 9.8, exploited in the wild)
- [CVE-2026-76268](https://insights.sbomify.com/CVE-2026-76268/): Missing Authentication for Critical Function in the Patroni REST API in Splunk Enterprise (critical 9.8)
- [CVE-2026-76284](https://insights.sbomify.com/CVE-2026-76284/): Improper Neutralization in Splunk Enterprise (critical 9.8)
- [CVE-2026-76285](https://insights.sbomify.com/CVE-2026-76285/): Improper Adherence to Coding Standards in Splunk Enterprise (critical 9.8)
- [CVE-2017-17067](https://insights.sbomify.com/CVE-2017-17067/): Auth bypass in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76258 and fix it if it is affected.

What it is: CVE-2026-76258 is a medium-severity vulnerability in Splunk Splunk, published on 19 Aug 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-2026-76258 in the wild and no public exploit code.

Affected product: Splunk Splunk. 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-2026-76258/ (Markdown: https://insights.sbomify.com/CVE-2026-76258/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76258
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76258
- OSV: https://osv.dev/vulnerability/CVE-2026-76258

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76258/
Summaries are generated and may contain mistakes; the official description above is the record.