CVE intelligence and bounded remediation

CVE-2020-1917 — Facebook Hhvm security vulnerability

Critical CVSS 9.8

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.

Severity
Critical
CVSS
9.8 (3.1)
Published
2021-03-10
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-122, CWE-787

Affected products

  • facebook / hhvm
  • facebook / hhvm / 4.94.0
  • facebook / hhvm / 4.95.0
  • facebook / hhvm / 4.96.0
  • facebook / hhvm / 4.97.0
  • facebook / hhvm / 4.98.0

Showing 6 representative product identities from 8 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Buffer bounds, memory safety, and memory corruption

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Check exposure

  • Identify affected native-code versions, build flags, architectures, parsers, codecs, drivers, and input paths in all shipped artifacts.
  • Determine whether untrusted data reaches the affected routine and the process privilege, sandbox, and network exposure.
  • Confirm statically linked, vendored, firmware, and platform-provided copies, not only package-manager records.

Remediate safely

  • Apply the maintained upstream correction or replace the affected component, then rebuild every dependent artifact from clean inputs.
  • Adopt bounds-checked interfaces, validated sizes and integer conversions, clear ownership, and memory-safe components where practical.
  • Enable supported compiler and runtime hardening and add sanitized tests and fuzz regression seeds derived from non-weaponized fixtures.

Authoritative sources

Complete CVE record and remediation plan

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