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Exploited vulnerability · CISA KEV

Is CVE-2021-21017 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Adobe Acrobat and Reader · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-21017, Adobe Acrobat and Reader Heap-based Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 265 days after it was published. It affects Adobe Acrobat and Reader. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021
ransomwareNot knownno confirmed use
EPSStop 1%among the most likely CVEs to be exploited
severity8.8CVSS 3.1 · high
US federal due17 Nov 2021BOD 22-01 deadline

What it is

Acrobat Acrobat and Reader contain a heap-based buffer overflow vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

VendorAdobe (83 exploited CVEs in KEV)
ProductAcrobat and Reader
VulnerabilityAdobe Acrobat and Reader Heap-based Buffer Overflow Vulnerability
WeaknessCWE-122
Published11 Feb 2021
Added to KEV3 Nov 2021
Reported by (CNA)adobe

What to do

  1. Check whether you run it. Look for Acrobat and Reader in your asset inventory, including appliances and cloud images. Stack check lists every exploited Adobe CVE at once.
  2. Apply the fix. Apply updates per vendor instructions.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 11 Feb 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Adobe.

Other exploited CVEs in Acrobat and Reader

References

Questions

Is CVE-2021-21017 being exploited?

Yes. CISA added CVE-2021-21017 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-21017 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-21017?

Apply updates per vendor instructions. Check Adobe's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Acrobat and Reader and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Adobe scorecard · act-now radar.

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