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CVE Record

CVE-2021-45931: HarfBuzz 2.9.0 has an out-of-bounds write in hb_bit_set_invertible_t::set (called from hb_sparseset_t<hb_bi...

HarfBuzz 2.9.0 has an out-of-bounds write in hb_bit_set_invertible_t::set (called from hb_sparseset_t<hb_bit_set_invertible_t>::set and hb_set_copy).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-45931 is a HarfBuzz 2.9.0 memory corruption issue: an out-of-bounds write in set handling. HarfBuzz is a dependency, so exposure depends on where that exact library version is packaged or linked. The provided sources do not include CVSS scoring or confirmed active exploitation.

Executive priority

Handle as a dependency hygiene issue with uncertain severity. It is not KEV-listed in the supplied data, but memory corruption in a common library justifies timely patch validation, especially where untrusted content is processed.

Technical view

The flaw is an out-of-bounds write in hb_bit_set_invertible_t::set, reachable through hb_sparseset_t<hb_bit_set_invertible_t>::set and hb_set_copy. The source bundle links OSS-Fuzz reporting, an upstream HarfBuzz commit, and Fedora and Gentoo advisories. Impact details are not fully described in the provided sources.

Likely exposure

Systems, applications, or Linux distribution packages using HarfBuzz 2.9.0 may be exposed. Fedora and Gentoo advisories indicate downstream package impact, but the bundle does not enumerate all affected products or fixed versions.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. Evidence points to fuzzing discovery and vendor remediation activity, not confirmed real-world attacks. Treat exploitability details as incomplete unless vendor guidance adds more context.

Researcher notes

Key gaps are missing CVSS, CWE, full affected-version range, and exploitation prerequisites. Use the OSS-Fuzz issue, OSV entry, upstream commit, and distribution advisories to map exact package impact without assuming broader product exposure.

Mitigation direction

  • Inventory HarfBuzz versions across OS packages, containers, and bundled application dependencies.
  • Update HarfBuzz through vendor-supported packages or guidance referenced by your distribution.
  • Prioritize systems that process untrusted fonts, documents, or text-rendering inputs.
  • Monitor HarfBuzz, Fedora, and Gentoo advisories for fixed-version details.
  • Avoid unsupported manual library swaps outside normal package-management controls.

Validation and detection

  • Confirm whether HarfBuzz 2.9.0 is installed or bundled in deployed software.
  • Check package changelogs against the referenced upstream HarfBuzz commit.
  • Verify Fedora or Gentoo hosts received the relevant advisory updates.
  • Review SBOMs and container images for embedded HarfBuzz copies.
  • Document any systems still pending vendor-supported remediation.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-45931 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
8Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.