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PatchSiren cyber security CVE debrief

CVE-2019-17026 Mozilla CVE debrief

CVE-2019-17026 is a Mozilla Firefox and Thunderbird type confusion vulnerability that CISA lists in its Known Exploited Vulnerabilities catalog. Because it is a KEV entry, defenders should treat it as a patch-priority issue and follow vendor update guidance promptly.

Vendor
Mozilla
Product
Firefox and Thunderbird
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Administrators and security teams responsible for Mozilla Firefox and Thunderbird deployments should review this CVE, especially where rapid patching and software inventory are part of routine endpoint management.

Technical summary

The supplied official records identify the issue as a type confusion vulnerability affecting Mozilla Firefox and Thunderbird. CISA added the CVE to its Known Exploited Vulnerabilities catalog on 2021-11-03 and lists the required action as applying updates per vendor instructions. The provided corpus does not include deeper technical impact details, so this debrief limits itself to the official identification and exploitation status.

Defensive priority

High. CISA KEV inclusion indicates known exploitation and makes this a priority for remediation planning and verification.

Recommended defensive actions

  • Apply the latest vendor updates for Mozilla Firefox and Thunderbird as directed by the vendor.
  • Inventory environments to confirm whether Firefox or Thunderbird are installed and where they are in use.
  • Prioritize remediation on systems that are broadly deployed or exposed to higher-risk user activity.
  • Verify patch completion after remediation and track any remaining versions that still need updates.

Evidence notes

This debrief uses only the supplied official sources: the CVE record, NVD detail page, and CISA KEV catalog/source item. The records explicitly identify the vulnerability as a type confusion issue in Mozilla Firefox and Thunderbird and state that CISA added it to KEV on 2021-11-03 with the action 'Apply updates per vendor instructions.' No CVSS score was supplied, and no exploit mechanics were inferred beyond the official listing.

Sources and references

Verified primary and authoritative sources

  • CVE-2019-17026 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2019-17026

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2019-17026 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2019-17026

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.