# CVE-2026-26201: emp3r0r Affected by Concurrent Map Access DoS (panic/crash)

> Concurrent map access without synchronization causes the emp3r0r C2 server to crash, resulting in denial of service.

- **Severity:** High 7.0 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Feb 2026
- **Updated:** 19 Feb 2026
- **Also known as:** GHSA-f5p9-j34q-pwcc, GO-2026-4504

## What is CVE-2026-26201?

CVE-2026-26201 is a high-severity vulnerability in jm33-m0 emp3r0r, published on 19 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

emp3r0r is a C2 designed by Linux users for Linux environments. Prior to version 3.21.2, multiple shared maps are accessed without consistent synchronization across goroutines. Under concurrent activity, Go runtime can trigger `fatal error: concurrent map read and map write`, causing C2 process crash (availability loss). Version 3.21.2 fixes this issue.

Weakness: CWE-663 (Use of a Non-reentrant Function in a Concurrent Context), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-26201?

3 open source packages ship an affected version, including github.com/jm33-m0/emp3r0r/core. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/jm33-m0/emp3r0r/core` | Go | All versions | 0.0.0-20260212232424-ea4d074f081d |
| `github.com/jm33-m0/emp3r0r/core` | Go | All versions | 0.0.0-20260212232424-ea4d074f081d |
| `github.com/jm33-m0/emp3r0r/core` | Go | All versions | 0.0.0-20260212232424-ea4d074f081d |

Products: Jm33-M0 Emp3r0r.

## How do I fix CVE-2026-26201?

Upgrade github.com/jm33-m0/emp3r0r/core to 0.0.0-20260212232424-ea4d074f081d or later.

## Is CVE-2026-26201 being exploited?

There is no known exploitation of CVE-2026-26201 in the wild and no public exploit code.

## Other vulnerabilities in jm33-m0 emp3r0r

- [CVE-2026-26068](https://insights.sbomify.com/CVE-2026-26068/): emp3r0r Agent-Controlled Metadata to Operator RCE (tmux Command Injection) (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-26201 and fix it if it is affected.

What it is: CVE-2026-26201 is a high-severity vulnerability in jm33-m0 emp3r0r, published on 19 Feb 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-2026-26201 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/jm33-m0/emp3r0r/core (Go): affected all versions; fixed in 0.0.0-20260212232424-ea4d074f081d
- github.com/jm33-m0/emp3r0r/core (Go): affected all versions; fixed in 0.0.0-20260212232424-ea4d074f081d
- github.com/jm33-m0/emp3r0r/core (Go): affected all versions; fixed in 0.0.0-20260212232424-ea4d074f081d

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-2026-26201/ (Markdown: https://insights.sbomify.com/CVE-2026-26201/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26201
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26201
- OSV: https://osv.dev/vulnerability/CVE-2026-26201

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26201/
Summaries are generated and may contain mistakes; the official description above is the record.