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PatchSiren cyber security CVE debrief

CVE-2021-21017 Adobe CVE debrief

CVE-2021-21017 is a known exploited vulnerability in Adobe Acrobat and Reader described as a heap-based buffer overflow. CISA added it to the Known Exploited Vulnerabilities catalog on 2021-11-03 and set a remediation due date of 2021-11-17. Organizations and individuals running Acrobat or Reader should prioritize vendor updates.

Vendor
Adobe
Product
Acrobat and Reader
CVSS
HIGH 8.8
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

IT and security teams, endpoint administrators, and any organization or individual using Adobe Acrobat or Adobe Reader, especially on systems that regularly open untrusted PDFs or handle external document workflows.

Technical summary

The supplied corpus identifies CVE-2021-21017 as a heap-based buffer overflow affecting Adobe Acrobat and Reader. CISA lists it as a known exploited vulnerability and directs affected users to apply updates per vendor instructions. No CVSS score, affected-version range, or further technical exploitation details were included in the provided corpus.

Defensive priority

High. Because CISA placed this CVE in the Known Exploited Vulnerabilities catalog, it should be treated as urgent patching work with the KEV due date used as a strong remediation target.

Recommended defensive actions

  • Apply Adobe updates per vendor instructions as soon as possible.
  • Inventory endpoints and servers that have Adobe Acrobat or Reader installed.
  • Prioritize remediation on high-risk or widely used systems first.
  • Verify remediation by confirming the installed Adobe version matches the vendor-fixed release.
  • Monitor CISA KEV and Adobe advisories for any follow-up guidance.

Evidence notes

This debrief is based only on the supplied CISA KEV entry and the official links provided in the corpus. The corpus confirms the CVE ID, Adobe Acrobat and Reader as the affected product, the vulnerability class as a heap-based buffer overflow, KEV listing status, date added (2021-11-03), and due date (2021-11-17). No additional exploit details, affected-version ranges, or CVSS data were present in the supplied source material.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-21017 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-21017

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

  • CVE-2021-21017 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-21017

    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.