How severe is GHSA-625h-95r8-8xpm?

GHSA-625h-95r8-8xpm has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-625h-95r8-8xpm?

GHSA-625h-95r8-8xpm affects the following packages: rack (RubyGems). Ecosystems affected: RubyGems.

How do I fix GHSA-625h-95r8-8xpm?

Update rack to 2.2.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-625h-95r8-8xpm is resolved across your whole dependency graph.

How do I detect GHSA-625h-95r8-8xpm 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-625h-95r8-8xpm 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-625h-95r8-8xpm?

O3 pinpoints whether GHSA-625h-95r8-8xpm 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-625h-95r8-8xpm actively exploited in the wild?

No public exploit code has been indexed for GHSA-625h-95r8-8xpm 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-625h-95r8-8xpm?

GHSA-625h-95r8-8xpm has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 41th 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-625h-95r8-8xpm?

GHSA-625h-95r8-8xpm is classified as Uncontrolled Resource Consumption (CWE-400), CWE-770 (CWE-770). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-625h-95r8-8xpm published, and has it been updated?

GHSA-625h-95r8-8xpm was published on September 25, 2025 and was last updated on April 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-625h-95r8-8xpm

HIGH

Rack has an unsafe default in Rack::QueryParser allows params_limit bypass via semicolon-separated parameters

Also known asCVE-2025-59830

Published

Sep 25, 2025

Updated

Apr 4, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk41th percentile+0.39%

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

1 pkg affected

💎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::QueryParser in version < 2.2.18 enforces its params_limit only for parameters separated by &, while still splitting on both & and ;. As a result, attackers could use ; separators to bypass the parameter count limit and submit more parameters than intended.

Details

The issue arises because Rack::QueryParser#check_query_string counts only & characters when determining the number of parameters, but the default separator regex DEFAULT_SEP = /[&;] */n splits on both & and ;. This mismatch means that queries using ; separators were not included in the parameter count, allowing params_limit to be bypassed.

Other safeguards (bytesize_limit and key_space_limit) still applied, but did not prevent this particular bypass.

Impact

Applications or middleware that directly invoke Rack::QueryParser with its default configuration (no explicit delimiter) could be exposed to increased CPU and memory consumption. This can be abused as a limited denial-of-service vector.

Rack::Request, the primary entry point for typical Rack applications, uses QueryParser in a safe way and does not appear vulnerable by default. As such, the severity is considered low, with the impact limited to edge cases where QueryParser is used directly.

Mitigation

Upgrade to a patched version of Rack where both & and ; are counted consistently toward params_limit.
If upgrading is not immediately possible, configure QueryParser with an explicit delimiter (e.g., &) to avoid the mismatch.
As a general precaution, enforce query string and request size limits at the web server or proxy layer (e.g., Nginx, Apache, or a CDN) to mitigate excessive parsing overhead.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`rack`	all versions	2.2.18

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 2.2.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-625h-95r8-8xpm 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-625h-95r8-8xpm 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-625h-95r8-8xpm. 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::QueryParser` in version `< 2.2.18` enforces its `params_limit` only for parameters separated by `&`, while still splitting on both `&` and `;`. As a result, attackers could use `;` separators to bypass the parameter count limit and submit more parameters than intended. ## Details The issue arises because `Rack::QueryParser#check_query_string` counts only `&` characters when determining the number of parameters, but the default separator regex `DEFAULT_SEP = /[&;] */n` splits on both `&` and `;`. This mismatch means that queries using `;` separators were not included in the

O3 Security · Impact-Aware SCA

Is GHSA-625h-95r8-8xpm in your dependencies?

O3 detects GHSA-625h-95r8-8xpm 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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