CVE-2021-36977Network attack vector

Heap overflow via H5MM_memcpy

Published Jul 20, 2021 · Updated Aug 4, 2024

Out-of-bounds write in matio 1.5.20 and 1.5.21 allows attackers to interrupt service via a crafted MAT file. The H5MM_memcpy routine copies HDF5-backed data without adequate heap bounds validation when reached through H5MM_malloc and H5C_load_entry, allowing a malformed MATLAB MAT file to overrun heap memory. Exploitation requires an application to parse attacker-supplied MAT data; the documented consequence is a process crash or service interruption, with no evidence of data disclosure or modification.

CVSS severity6.5
Medium
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in matio 1.5.20 and 1.5.21 allows attackers to interrupt service via a crafted MAT file. The H5MM_memcpy routine copies HDF5-backed data without adequate heap bounds validation when reached through H5MM_malloc and H5C_load_entry, allowing a malformed MATLAB MAT file to overrun heap memory. Exploitation requires an application to parse attacker-supplied MAT data; the documented consequence is a process crash or service interruption, with no evidence of data disclosure or modification.

The record

CVE
CVE-2021-36977
Published
Jul 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NISTAV:N/AC:M/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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