CVE-2021-24036Network attack vector

Remote code execution via IOBuf size overflow

Published Jul 23, 2021 · Updated Aug 3, 2024

Heap overflow in affected Folly and HHVM releases allows remote attackers to execute code by supplying an attacker-controlled IOBuf size. IOBuf allocation and reserve paths add capacity, headroom, and tailroom values without checked arithmetic, allowing the calculated heap allocation size to wrap before data is written. Reachability requires HHVM or another Folly consumer to pass remotely controlled size data into these paths, and successful corruption grants code execution in that process.

CVSS severity9.8
Critical
EPSS probability3.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap overflow in affected Folly and HHVM releases allows remote attackers to execute code by supplying an attacker-controlled IOBuf size. IOBuf allocation and reserve paths add capacity, headroom, and tailroom values without checked arithmetic, allowing the calculated heap allocation size to wrap before data is written. Reachability requires HHVM or another Folly consumer to pass remotely controlled size data into these paths, and successful corruption grants code execution in that process.

The record

CVE
CVE-2021-24036
Published
Jul 23, 2021
Updated
Aug 3, 2024
Vendor
Meta Platforms, Inc.
Product
HHVM
Classifications
CWE-122, CWE-190, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.102.0 <unspecified
  2. Affected versionversion=4.113.0
  3. Affected versionversion=4.114.0
  4. Affected versionversion=4.115.0
  5. Affected versionversion=4.116.0
  6. Affected versionversion=4.117.0
  7. Affected versionversion=4.118.0 <unspecified
  8. Affected versionversion=4.81.0 <unspecified
  9. Affected versionversion=unspecified <4.80.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Meta Platforms, Inc. · HHVMversion=4.102.0 <unspecified; version=4.113.0; version=4.114.0; version=4.115.0; version=4.116.0; version=4.117.0; version=4.118.0 <unspecified; version=4.81.0 <unspecified; version=unspecified <4.80.5
Meta Platforms, Inc. · Follyversion=unspecified <v2021.07.22.00

Published CVSS scores

9.8UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-190Integer Overflow or Wraparound
T1190Exploit Public-Facing Application

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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