# CVE-2025-27421: Goroutine Leak in Abacus SSE Implementation

> Attackers can cause resource exhaustion and denial of service by disconnecting from the SSE stream, preventing new connections.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Mar 2025
- **Updated:** 3 Mar 2025
- **Also known as:** GHSA-vh64-54px-qgf8, GO-2025-3498

## What is CVE-2025-27421?

CVE-2025-27421 is a high-severity denial of service vulnerability in JasonLovesDoggo abacus, published on 3 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Abacus is a highly scalable and stateless counting API. A critical goroutine leak vulnerability has been identified in the Abacus server's Server-Sent Events (SSE) implementation. The issue occurs when clients disconnect from the /stream endpoint, as the server fails to properly clean up resources and terminate associated goroutines. This leads to resource exhaustion where the server continues running but eventually stops accepting new SSE connections while maintaining high memory usage. The vulnerability specifically involves improper channel cleanup in the event handling mechanism, causing goroutines to remain blocked indefinitely. This vulnerability is fixed in 1.4.0.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2025-27421?

3 open source packages ship an affected version, including github.com/jasonlovesdoggo/abacus.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/jasonlovesdoggo/abacus` | Go | All versions | 0.0.0-20250302043802-898ff1204e11 |
| `github.com/jasonlovesdoggo/abacus` | Go | All versions | 0.0.0-20250302043802-898ff1204e11 |
| `github.com/jasonlovesdoggo/abacus` | Go | All versions | 0.0.0-20250302043802-898ff1204e11 |

## How do I fix CVE-2025-27421?

Upgrade github.com/jasonlovesdoggo/abacus to 0.0.0-20250302043802-898ff1204e11 or later.

## Is CVE-2025-27421 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-27421 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-27421 and fix it if it is affected.

What it is: CVE-2025-27421 is a high-severity denial of service vulnerability in JasonLovesDoggo abacus, published on 3 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-27421 exists.

Affected packages and fixed versions:
- github.com/jasonlovesdoggo/abacus (Go): affected all versions; fixed in 0.0.0-20250302043802-898ff1204e11
- github.com/jasonlovesdoggo/abacus (Go): affected all versions; fixed in 0.0.0-20250302043802-898ff1204e11
- github.com/jasonlovesdoggo/abacus (Go): affected all versions; fixed in 0.0.0-20250302043802-898ff1204e11

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-2025-27421/ (Markdown: https://insights.sbomify.com/CVE-2025-27421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-27421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-27421
- OSV: https://osv.dev/vulnerability/CVE-2025-27421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-27421/
Summaries are generated and may contain mistakes; the official description above is the record.