CVE-2020-1899Network attack vector

Memory disclosure via APC-only serialization type

Published Mar 11, 2021 · Updated Aug 4, 2024

Untrusted pointer dereference in affected HHVM releases allows remote attackers to read process memory through crafted serialized data. VariableUnserializer accepts the APC-only S type during normal unserialize() calls and treats attacker-supplied numeric data as a static StringData address. No authentication or user interaction is required when an exposed application passes remote input to unserialize(), and disclosure is limited to memory readable by the HHVM process.

CVSS severity7.5
High
EPSS probability1.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Untrusted pointer dereference in affected HHVM releases allows remote attackers to read process memory through crafted serialized data. VariableUnserializer accepts the APC-only S type during normal unserialize() calls and treats attacker-supplied numeric data as a static StringData address. No authentication or user interaction is required when an exposed application passes remote input to unserialize(), and disclosure is limited to memory readable by the HHVM process.

The record

CVE
CVE-2020-1899
Published
Mar 11, 2021
Updated
Aug 4, 2024
Vendor
Meta Platforms, Inc.
Product
HHVM
Classifications
CWE-119, CWE-822, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 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?

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

  1. Affected versionversion=4.33.0 <unspecified
  2. Affected versionversion=4.57.0
  3. Affected versionversion=4.58.0 <unspecified
  4. Affected versionversion=4.59.0
  5. Affected versionversion=4.60.0
  6. Affected versionversion=4.61.0
  7. Affected versionversion=4.62.0
  8. Affected versionversion=unspecified <4.32.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Meta Platforms, Inc. · HHVMversion=4.33.0 <unspecified; version=4.57.0; version=4.58.0 <unspecified; version=4.59.0; version=4.60.0; version=4.61.0; version=4.62.0; version=unspecified <4.32.3

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-822Untrusted Pointer Dereference
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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