LiveActive security incident?Get immediate response
CVE Record

CVE-2021-29980: Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption...

Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This Mozilla flaw could let a malformed canvas-related operation corrupt memory and crash Firefox or Thunderbird. Mozilla described the crash as potentially exploitable. The business risk is mainly from outdated browsers or mail clients still below the fixed release lines.

Executive priority

Prioritize remediation where outdated Mozilla clients are still present. This is not KEV-backed emergency work, but browser and mail-client memory corruption can become high-impact if legacy endpoints remain exposed.

Technical view

CVE-2021-29980 is uninitialized memory in a canvas object causing an incorrect free() and memory corruption. Affected versions are Firefox before 91, Firefox ESR before 78.13, Thunderbird before 78.13, and Thunderbird before 91. The bundle provides no CVSS, CWE, or detailed attack vector.

Likely exposure

Exposure is likely on endpoints running old Mozilla Firefox, Firefox ESR, or Thunderbird versions. Organizations with unmanaged desktops, legacy ESR deployments, or delayed Linux package updates should prioritize inventory checks.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation evidence. Mozilla states the issue could cause a potentially exploitable crash, but the bundle does not provide proof-of-concept status or exploitation details.

Researcher notes

Evidence supports a memory safety issue with potentially exploitable crash behavior, but not active exploitation. The source bundle lacks CVSS, CWE classification, patch commit detail, and attack-vector specifics, so validation should focus on version exposure and vendor advisory alignment.

Mitigation direction

  • Upgrade Firefox to version 91 or later.
  • Upgrade Firefox ESR to version 78.13 or later.
  • Upgrade Thunderbird to version 78.13, 91, or later.
  • Apply relevant Linux distribution security updates.
  • Check Mozilla and distro advisories for any environment-specific guidance.

Validation and detection

  • Inventory endpoint Firefox, Firefox ESR, and Thunderbird versions.
  • Confirm no deployed version is below the fixed release threshold.
  • Check software management and package manager compliance reports.
  • Review unmanaged or BYOD endpoints for outdated Mozilla clients.
  • Document exceptions for unsupported or pinned legacy versions.
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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-29980 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
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
MozillaThunderbirdunspecified, unspecifiedListed
MozillaFirefox ESRunspecifiedListed
MozillaFirefoxunspecifiedListed
Weakness

CWE details

No CWE listed

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