How severe is GHSA-6xw4-3v39-52mm?

GHSA-6xw4-3v39-52mm has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-6xw4-3v39-52mm?

GHSA-6xw4-3v39-52mm affects the following packages: rack (RubyGems), rack (RubyGems), rack (RubyGems). Ecosystems affected: RubyGems.

How do I fix GHSA-6xw4-3v39-52mm?

Update rack to 2.2.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6xw4-3v39-52mm is resolved across your whole dependency graph.

How do I detect GHSA-6xw4-3v39-52mm in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-6xw4-3v39-52mm if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-6xw4-3v39-52mm?

O3 pinpoints whether GHSA-6xw4-3v39-52mm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-6xw4-3v39-52mm actively exploited in the wild?

No public exploit code has been indexed for GHSA-6xw4-3v39-52mm yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-6xw4-3v39-52mm?

GHSA-6xw4-3v39-52mm has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 44th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-6xw4-3v39-52mm?

GHSA-6xw4-3v39-52mm is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-6xw4-3v39-52mm published, and has it been updated?

GHSA-6xw4-3v39-52mm was published on October 10, 2025 and was last updated on February 4, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎 RubyGems

GHSA-6xw4-3v39-52mm

HIGH

Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing

Also known asCVE-2025-61919

Published

Oct 10, 2025

Updated

Feb 4, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk44th percentile+0.31%

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.

Blast Radius

3 pkgs affected

💎rack💎rack💎rack

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Rack::Request#POST reads the entire request body into memory for Content-Type: application/x-www-form-urlencoded, calling rack.input.read(nil) without enforcing a length or cap. Large request bodies can therefore be buffered completely into process memory before parsing, leading to denial of service (DoS) through memory exhaustion.

Details

When handling non-multipart form submissions, Rack’s request parser performs:

form_vars = get_header(RACK_INPUT).read

Since read is called with no argument, the entire request body is loaded into a Ruby String. This occurs before query parameter parsing or enforcement of any params_limit. As a result, Rack applications without an upstream body-size limit can experience unbounded memory allocation proportional to request size.

Impact

Attackers can send large application/x-www-form-urlencoded bodies to consume process memory, causing slowdowns or termination by the operating system (OOM). The effect scales linearly with request size and concurrency. Even with parsing limits configured, the issue occurs before those limits are enforced.

Mitigation

Update to a patched version of Rack that enforces form parameter limits using query_parser.bytesize_limit, preventing unbounded reads of application/x-www-form-urlencoded bodies.
Enforce strict maximum body size at the proxy or web server layer (e.g., Nginx client_max_body_size, Apache LimitRequestBody).

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`rack`	all versions	2.2.20
💎RubyGems	`rack`	≥ 3.0&&< 3.1.18	3.1.18
💎RubyGems	`rack`	≥ 3.2&&< 3.2.3	3.2.3

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update rack to 2.2.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6xw4-3v39-52mm 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 pinpoints whether GHSA-6xw4-3v39-52mm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-6xw4-3v39-52mm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary `Rack::Request#POST` reads the entire request body into memory for `Content-Type: application/x-www-form-urlencoded`, calling `rack.input.read(nil)` without enforcing a length or cap. Large request bodies can therefore be buffered completely into process memory before parsing, leading to denial of service (DoS) through memory exhaustion. ## Details When handling non-multipart form submissions, Rack’s request parser performs: ```ruby form_vars = get_header(RACK_INPUT).read ``` Since `read` is called with no argument, the entire request body is loaded into a Ruby `String`. This o

O3 Security · Impact-Aware SCA

Is GHSA-6xw4-3v39-52mm in your dependencies?

O3 detects GHSA-6xw4-3v39-52mm across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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