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Multiple Exploits for Adobe Acrobat XI Vulnerabilities Disclosed

Multiple Exploits for Adobe Acrobat XI Vulnerabilities Disclosed

First seen 12 Nov 2026, 18:46 UTC • •
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ThreatCluster AI
ThreatCluster •November 12, 2026 at 18:47 UTC
  • •Multiple unverified PoC exploits released for Adobe Acrobat XI vulnerabilities.
  • •CVE-2021-28550 and CVE-2021-21017 are under active exploitation.
  • •Exploits are intended for lab use and require isolated environments.

A series of proof-of-concept (PoC) exploits have been released for vulnerabilities in Adobe Acrobat XI, including CVE-2021-21017 (Heap Buffer Overflow), CVE-2021-28550 (Use-After-Free), CVE-2018-4990 (Double Free), and CVE-2023-26369 (Out-of-Bounds Write). All exploits are categorized as unverified and are based on generic legacy-module templates from Metasploit, which have not been validated against the specific CVEs. The vulnerabilities affect Adobe Acrobat XI, which is known to have been under, particularly CVE-2021-28550 and CVE-2021-21017, both added to the CISA KEV list in November 2021. The current status indicates that while PoCs exist, they are intended for lab use only and require isolated environments for testing. Security professionals are advised to monitor these vulnerabilities closely due to their potential impact on systems still using Adobe Acrobat XI.

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Timeline

2018-07-09
CVE-2018-4990 published
Vulnerability assigned a CVE identifier and published in the National Vulnerability Database.
MITRE
2021-09-02
CVE-2021-28550 published
Adobe disclosed a critical Use-After-Free vulnerability affecting Acrobat XI.
Sploitus
2021-11-03
CVE-2021-21017 and CVE-2021-28550 added to CISA KEV
Both vulnerabilities were recognized for active exploitation, prompting their addition to the KEV catalog.
Sploitus
2023-09-14
CVE-2023-26369 added to CISA KEV
Adobe Acrobat XI's Out-of-Bounds Write vulnerability was recognized for active exploitation.
Sploitus

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Common questions

Which CVEs are involved?
The vulnerabilities include CVE-2021-21017, CVE-2021-28550, CVE-2018-4990, and CVE-2023-26369.
Are these vulnerabilities actively exploited?
Yes, CVE-2021-28550 and CVE-2021-21017 have been confirmed as actively exploited.
What should organizations do to protect themselves?
Organizations should monitor these vulnerabilities and consider upgrading from Adobe Acrobat XI if still in use.