CVE-2023-2512Network attack vector

Runtime crash via FormData element-count overflow

Published May 12, 2023 · Updated Jan 24, 2025

Buffer under-read in Cloudflare workerd before 1.20230419.0 allows remote attackers to crash the runtime via a huge form request. The FormData forEach() element counter overflows above 2^31 entries, causing iteration to read from the wrong memory location. Reachability requires about 160 GB of allocatable memory, a form-encoded request at least tens of gigabytes long, and application code that invokes request.formData() followed by formData.forEach(); other undefined behavior remains theoretical.

CVSS severity6.5
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer under-read in Cloudflare workerd before 1.20230419.0 allows remote attackers to crash the runtime via a huge form request. The FormData forEach() element counter overflows above 2^31 entries, causing iteration to read from the wrong memory location. Reachability requires about 160 GB of allocatable memory, a form-encoded request at least tens of gigabytes long, and application code that invokes request.formData() followed by formData.forEach(); other undefined behavior remains theoretical.

The record

CVE
CVE-2023-2512
Published
May 12, 2023
Updated
Jan 24, 2025
Vendor
Cloudflare
Product
workerd
Classifications
CWE-127, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 12, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 24, 2025Record 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=v1.20221108.0 <=v1.20230404.0 changes=[{"at":"v1.20230419.0","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · workerdversion=v1.20221108.0 <=v1.20230404.0 changes=[{"at":"v1.20230419.0","status":"unaffected"}]

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H

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-127Buffer Under-read
T1499.004Application or System Exploitation

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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