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Vulnerability record · CVE-2020-1917 · published 10 March 2021

CVE-2020-1917: Facebook hhvm heap-based buffer overflow vulnerability

Facebook · Hhvm

xbuf_format_converter, used as part of exif_read_data, was appending a terminating null character to the generated string, but was not using its standard append char function. As a result, if the buffer was full, it would result in an out-of-bounds write. This issue affects HHVM versions prior to 4.56.3, all versions between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.

9.8 CVSS 3.1 Critical EPSS 1.4% · top 28.9% CWE-122 · Heap-based buffer overflowCWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 7.5
1.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

xbuf_format_converter, used as part of exif_read_data, was appending a terminating null character to the generated string, but was not using its standard append char function. As a result, if the buffer was full, it would result in an out-of-bounds write. This issue affects HHVM versions prior to 4.56.3, all versions between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/facebook/hhvm/commit/08193b7f0cd3910256e00d599f0f3eb2519c44ca PatchThird Party Advisory
https://hhvm.com/blog/2021/02/25/security-update.html Release NotesVendor Advisory
https://github.com/facebook/hhvm/commit/08193b7f0cd3910256e00d599f0f3eb2519c44ca PatchThird Party Advisory
https://hhvm.com/blog/2021/02/25/security-update.html Release NotesVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-1917), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.