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CVE-2021-28550· NVD / CVE Program· CNA adobe

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

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.

HighCVSS 8.8 · v3.1KEVWeaponized No fix recorded
Published
Sep 2, 2021
Updated
Jun 16, 2026
EPSS
52.0% · 99th percentile
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Action score

81

Now

Patch today or shut off access.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
30 / 30 · Listed
EPSS
16 / 30 · 52.0%

CISA SSVC decision

Exploitation
active
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
8.8
CNA · adobe
9.6
0.8 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for government agencies: Nov 17, 2021.

Noroxi analysis

No Noroxi analysis for this record yet

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We use this product, ask for help

Affected systems

VendorProduct
adobeacrobat dc
adobeacrobat reader dc
adobeacrobat
adobeacrobat reader
microsoftwindows
applemacos

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • adobe acrobat17.011.30059 and later · up to 17.011.30194 inclusive
  • adobe acrobat20.001.30005 and later · up to 20.001.30020 inclusive
  • adobe acrobat dc15.008.20082 and later · up to 21.001.20150 inclusive
  • adobe acrobat dc15.008.20082 and later · up to 21.001.20149 inclusive
  • adobe acrobat reader17.011.30059 and later · up to 17.011.30194 inclusive
  • adobe acrobat reader20.001.30005 and later · up to 20.001.30020 inclusive
  • adobe acrobat reader dc15.008.20082 and later · up to 21.001.20150 inclusive
  • adobe acrobat reader dc15.008.20082 and later · up to 21.001.20149 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (adobe). Independent of NVD's CPE analysis and usually ahead of it.

  • Adobe Acrobat Reader

    • unspecified and later · up to and including 2020.001.30020affected
    • unspecified and later · up to and including 2021.001.20150affected
    • unspecified and later · up to and including 2017.011.30194affected
    • unspecified and later · up to and including Noneaffected

Same product

adobe: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-21608Adobe Acrobat Reader DC resetForm Use-After-Free Remote Code Execution VulnerabilityKEV
    79This week
  • CVE-2020-9715Adobe Acrobat and Reader versions 2020.009.20074 and earlier, 2020.001.30002, 2017.011.30171 and earlier, and 2015.006.30523 and earlier havKEV
    76This week
  • CVE-2018-4990Adobe Acrobat and Reader versions 2018.011.20038 and earlier, 2017.011.30079 and earlier, and 2015.006.30417 and earlier have a Double Free KEV
    76This week
  • CVE-2026-34621Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321)KEV
    65This week
  • CVE-2018-4993Adobe Acrobat and Reader versions 2018.011.20038 and earlier, 2017.011.30079 and earlier, and 2015.006.30417 and earlier have an NTLM SSO ha
    56Plan
  • CVE-2021-28560Adobe Acrobat Reader heap corruption vulnerability could lead to arbitrary code execution
    55Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. CISA KEV+61 d
  3. TodayOct 4, 2026+1858 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records