Background exploitation KEV catalog No authentication

CVE-2021-28550

Adobe Acrobat and Reader Use-After-Free Vulnerability

CheckOps priority index

7.8/10 Patch within 7 days

Severity9.6

Probability5.2

Exploitation4/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 51.9% higher than 98.9% of CVEs

CVSS 3.0 9.6 AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:

Exploited for 1,826 days 03 Nov 2021

CISA due date 17 Nov 2021 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 4 / 5

KEV catalog (CISA)03 Nov 2021
Exploited in EUVD (ENISA)03 Nov 2021
Used by ransomwareno
EPSS above 10 %51.9%
No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply updates per vendor instructions.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

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.

Affected products

Acrobat ReaderAcrobat and Reader

Affected versions

unspecified ≤2021.001.20150
unspecified ≤None
unspecified ≤2020.001.30020
unspecified ≤2017.011.30194

Weaknesses (CWE)

CWE-416

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

02 Sept 2021
Published
03 Nov 2021
Exploitation reported (ENISA)
03 Nov 2021
Added to the KEV catalog
17 Nov 2021
CISA remediation due date
26 Sept 2026
EPSS peak: 52.0%

References

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