CVE-2020-36401

Arbitrary code execution via failed reallocation double-free

Published Jul 1, 2021 · Updated Aug 4, 2024

Double free in mruby 2.1.2 allows context-dependent attackers to corrupt heap memory through a failed memory reallocation. In src/gc.c, mrb_realloc freed the original pointer when mrb_realloc_simple returned NULL, then raised an out-of-memory exception while an object still referenced that allocation. Reachability depends on a host application processing attacker-controlled Ruby input and entering this cleanup path; the resulting corruption can crash the host or enable code execution.

CVSS severity7.8
High
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double free in mruby 2.1.2 allows context-dependent attackers to corrupt heap memory through a failed memory reallocation. In src/gc.c, mrb_realloc freed the original pointer when mrb_realloc_simple returned NULL, then raised an out-of-memory exception while an object still referenced that allocation. Reachability depends on a host application processing attacker-controlled Ruby input and entering this cleanup path; the resulting corruption can crash the host or enable code execution.

The record

CVE
CVE-2020-36401
Published
Jul 1, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-415, T1203
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1203Exploitation for Client Execution

Public exploit references

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Technologies

Your stack

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Your stack

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