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Fencer Vulns
medium 6.5

CVE-2023-2512 json

Buffer under-read in workerd

published 2023-05-12 3 y ago modified 2026-07-08 4 mo ago also GHSA-8vx6-69vg-c46f , EUVD-2023-1504

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

Prior to version v1.20230419.0, the FormData API implementation was subject to an integer overflow. If a FormData instance contained more than 2^31 elements, the forEach() method could end up reading from the wrong location in memory while iterating over elements. This would most likely lead to a segmentation fault, but could theoretically allow arbitrary undefined behavior.

In order for the bug to be exploitable, the process would need to be able to allocate 160GB of RAM. Due to this, the bug was never exploitable on the Cloudflare Workers platform, but could theoretically be exploitable on deployments of workerd running on machines with a huge amount of memory. Moreover, in order to be remotely exploited, an attacker would have to upload a single form-encoded HTTP request of at least tens of gigabytes in size. The application code would then have to use request.formData() to parse the request and formData.forEach() to iterate over this data. Due to these limitations, the exploitation likelihood was considered Low.

A fix that addresses this vulnerability has been released in version v1.20230419.0 and users are encouraged to update to the latest version available.

Patch / fix

  • npm workerd 1.20230419.0
  • Cloudflare workerd v1.20230419.0

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
21 mo ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm workerd
<1.20230419.0
1.20230419.0

Affected products

  • Cloudflare workerd

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.