CVE-2025-27421 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in github.com/jasonlovesdoggo/abacus. A fix is available for github.com/jasonlovesdoggo/abacus — see the affected versions and patch details below.
Goroutine Leak in Abacus SSE Implementation
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-27421.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-27421 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/jasonlovesdoggo/abacusReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Goroutine Leak in Abacus SSE Implementation
Summary
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.
POC
Impact
This vulnerability affects all versions of Abacus prior to v1.4.0. The issue causes:
- Permanent unresponsiveness of the
/streamendpoint after prolonged use - Memory growth that stabilizes at a high level but prevents proper functionality
- Selective denial of service affecting only SSE connections while other endpoints remain functional
- Accumulated orphaned goroutines that cannot be garbage collected
- High resource consumption under sustained client connection/disconnection patterns
Systems running Abacus in production with client applications that frequently establish and terminate SSE connections are most vulnerable. The issue becomes particularly apparent in high-traffic environments or during connection stress testing.
Patches
The vulnerability has been patched in Abacus v1.4.0. The fix includes:
- Implementing buffered channels to prevent blocking operations during cleanup
- Adding proper mutex-protected cleanup logic to ensure resources are released exactly once
- Implementing timeout protection for channel operations to prevent deadlocks
- Ensuring consistent cleanup when connections terminate unexpectedly
- Adding improved monitoring for client disconnections using request context
- Restructuring the event broadcasting system to safely handle client removal
Users should upgrade to v1.4.0 or later versions as soon as possible.
Workarounds
If upgrading is not immediately possible, the following workarounds can help mitigate the issue:
-
Limit maximum connections: Configure your reverse proxy to limit the maximum number of concurrent connections to the
/streamendpoints. -
Implement request timeouts: Configure your infrastructure to terminate long-lived SSE connections after a reasonable period.
-
Restart regularly: Schedule regular restarts of the Abacus service to reclaim resources.
-
Monitor memory usage: Set up alerts for abnormal memory growth patterns.
-
Separate instance for SSE: Run a dedicated Abacus instance solely for handling SSE connections, allowing it to be restarted without affecting the main API functionality.
References
- Go Concurrency Patterns: Context
- CWE-772: Missing Release of Resource after Effective Lifetime
- OWASP Top 10: Resource Exhaustion
- Resource Management in Go
For More Information
Please contact the Abacus security team at [email protected] for additional information or to report further security issues.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/jasonlovesdoggo/abacus | all versions | 0.0.0-20250302043802-898ff1204e11go get github.com/jasonlovesdoggo/abacus@v0.0.0-20250302043802-898ff1204e11 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/jasonlovesdoggo/abacus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/jasonlovesdoggo/abacus to 0.0.0-20250302043802-898ff1204e11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27421 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-27421 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-27421. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-27421 in your dependencies?
O3 Security finds CVE-2025-27421 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.