CVE-2022-4996 Overview
CVE-2022-4996 affects mruby 3.1.0, a lightweight implementation of the Ruby programming language. The flaw resides in the udiv function of the bigint.c source file. The function performs a floating point comparison using an incorrect operator, classified under [CWE-1077] (Floating Point Comparison with Incorrect Operator). Attackers can trigger the flaw remotely by supplying crafted input that reaches the affected arithmetic routine. Public exploit details have been disclosed through Huntr and VulDB, increasing the likelihood of opportunistic abuse against embedded applications that rely on mruby. The vulnerability primarily impacts availability rather than confidentiality or integrity.
Critical Impact
Remote attackers can exploit an incorrect floating point comparison in mruby's udiv function to disrupt availability in applications embedding the affected interpreter.
Affected Products
- mruby 3.1.0
- Applications embedding the mruby 3.1.0 interpreter
- Downstream software distributing vulnerable mruby builds
Discovery Timeline
- 2026-08-20 - CVE-2022-4996 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2022-4996
Vulnerability Analysis
The flaw exists in the udiv function within bigint.c, part of mruby's big integer arithmetic implementation. The code compares floating point values using an operator that does not correctly account for floating point semantics. This produces incorrect branching behavior during division operations on large integers. When triggered, the miscomparison can lead to unexpected program state or termination inside the interpreter.
Because mruby is commonly embedded into larger applications, the effect surfaces wherever untrusted Ruby-like input can reach big integer arithmetic. The issue is reachable across the network when the embedding application exposes script evaluation or numeric parsing paths. The public exploit lowers the barrier for adversaries to reproduce the condition against exposed services.
Root Cause
The root cause is an incorrect operator choice for floating point comparison inside udiv, mapped to [CWE-1077]. Floating point values require operators that consider precision and rounding rather than direct equality or inequality logic used for integers. The affected comparison produces the wrong branch outcome, corrupting the arithmetic control flow within the big integer routine.
Attack Vector
Exploitation is network-reachable and requires no authentication or user interaction. An attacker submits crafted numeric input that flows into the udiv routine within an application embedding mruby 3.1.0. See the Huntr bounty listing and VulDB advisory for CVE-2022-4996 for reference material. No verified proof-of-concept code is reproduced here; consult the linked advisories for technical specifics.
Detection Methods for CVE-2022-4996
Indicators of Compromise
- Repeated crashes or aborts in processes embedding the mruby interpreter, particularly during arithmetic-heavy script execution.
- Log entries showing floating point exceptions or unexpected termination originating from bigint.c code paths.
- Anomalous input patterns targeting numeric parameters in services that evaluate mruby scripts.
Detection Strategies
- Inventory all applications and appliances that embed mruby and confirm the compiled version to identify exposure to 3.1.0.
- Monitor application telemetry for repeated interpreter faults tied to big integer division workloads.
- Deploy input validation logging on network-facing endpoints that accept numeric expressions or script fragments.
Monitoring Recommendations
- Aggregate crash telemetry from services embedding mruby into a central logging pipeline for correlation.
- Alert on unusual request volumes containing large numeric literals directed at script evaluation endpoints.
- Track upstream mruby project commits and advisories to detect additional related fixes.
How to Mitigate CVE-2022-4996
Immediate Actions Required
- Identify every deployment running mruby 3.1.0 or products bundling that release.
- Apply the upstream patch from the mruby project once integrated into your build pipeline.
- Restrict network exposure of services that evaluate untrusted Ruby-like input until patching completes.
Patch Information
The upstream mruby project addresses the incorrect floating point comparison in bigint.c. Rebuild embedded applications against a patched mruby revision. Reference the VulDB vulnerability overview and VulDB submission report for links to the corrective commit and affected code.
Workarounds
- Disable or gate script evaluation endpoints that expose mruby arithmetic to untrusted callers.
- Enforce strict input validation on numeric parameters before they reach the interpreter.
- Isolate processes embedding mruby using sandboxing or resource limits to contain crash impact.
# Configuration example
# Verify linked mruby version in an embedding binary
strings /path/to/application | grep -i "mruby"
# Apply resource limits to contain interpreter crashes
ulimit -c 0
systemctl edit my-mruby-service
# Add under [Service]:
# MemoryMax=512M
# Restart=on-failure
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
