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Fencer Vulns
critical 9.6

CVE-2021-28550 kev in the critical feed json

Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution

published 2021-09-02 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15226

cvss
9.6
version 3.0, CNA
cisa kev
Exploited
added 2021-11-03
epss
52.1%
EPSS 52.1% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and 2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Patch / fix

cisa required action Apply updates per vendor instructions.

  • tor Alpine 3.13 0.4.4.9-r0
  • tor Alpine 3.14 0.4.5.9-r0
  • tor Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 0.4.6.5-r0

alpine advisories ALPINE-CVE-2021-28550

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Timeline

  1. 0-day patched (Project Zero)
  2. Published
  3. Added to CISA KEV
  4. CISA patch deadline
  5. CISA SSVC: exploitation active

Known exploited

Added
5 y ago
Patch by
2021-11-17 (4 y ago)
Ransomware
Not known
Required action
Apply updates per vendor instructions.
Vendor, product
Adobe, Acrobat and Reader
CISA name
Adobe Acrobat and Reader Use-After-Free Vulnerability

Zero-day

Detected in real attacks while still unknown to the vendor and the public, per Google Project Zero's 0day In-the-Wild tracker.

Patched
2021-05-11
Details
project zero tracker

ATT&CK techniques

How it is exploited and what it leads to, in MITRE ATT&CK terms.

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
21 mo ago

Exploit prediction

52.13% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.0 9.6 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Adobe Acrobat Reader

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.