CVE-2021-21086: Adobe Reader CoolType Arbitrary Stack Manipulation
Noroxi assessment
Priority: Monitor (action score 32/100)
- Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
- Probability of exploitation in the next 30 days: 4.7% (FIRST EPSS); higher than 91.7% of all records.
- Someone with local access to the system 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.
- According to the record, no fixed version is available yet.
Low priority for now. Update when a fix is released; follow the vendor's advisory.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by an Out-of-bounds Write vulnerability in the CoolType library. 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.
- Published
- Sep 2, 2021
- Updated
- Jun 16, 2026
- EPSS
- 4.7% · 91th percentile
- CWE
- CWE-787
Report tools
Action score
32
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 4.7%
CNA vs NVD score
- NVD
- 7.8
- CNA · adobe
- 7.8
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- Proof of concept exists, no weaponized module
- No fixed version yet
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| adobe | acrobat | cpe:2.3:a:adobe:acrobat |
| adobe | acrobat dc | cpe:2.3:a:adobe:acrobat_dc |
| adobe | acrobat reader | cpe:2.3:a:adobe:acrobat_reader |
| adobe | acrobat reader dc | cpe:2.3:a:adobe:acrobat_reader_dc |
| apple | macos | cpe:2.3:o:apple:macos |
| microsoft | windows | cpe:2.3:o:microsoft:windows |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- adobe acrobat17.011.30056 and later · up to 17.011.30188 inclusive
- adobe acrobat20.001.30005 and later · up to 20.001.30018 inclusive
- adobe acrobat dc20.006.20042 and later · up to 20.013.20074 inclusive
- adobe acrobat reader17.011.30059 and later · up to 17.011.30188 inclusive
- adobe acrobat reader20.001.30005 and later · up to 20.001.300183 inclusive
- adobe acrobat reader dc20.006.20042 and later · up to 20.013.20074 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 2020.013.20074affected
- unspecified and later · up to and including 2020.001.30018affected
- unspecified and later · up to and including 2017.011.30188affected
- unspecified and later · up to and including Noneaffected
Same product
adobe: all recordsOther highest-scoring records for the same primary product.
- CVE-2011-2462Unspecified vulnerability in the U3D component in Adobe Reader and Acrobat 10.1.1 and earlier on Windows and Mac OS X, and Adobe Reader 9.x KEV96Now
- CVE-2013-3346Adobe Reader and Acrobat 9.x before 9.5.5, 10.x before 10.1.7, and 11.x before 11.0.03 allow attackers to execute arbitrary code or cause a KEV93Now
- CVE-2021-21017Acrobat Reader DC Heap-based Buffer Overflow Vulnerability Could Lead To Arbitrary Code ExecutionKEV91Now
Published before and after this one in the same product
- ← EarlierCVE-2021-28545Apr 1, 2021 · Acrobat Reader DC Missing Support for Integrity Check33Monitor
- ← EarlierCVE-2021-28546Apr 1, 2021 · Acrobat Reader DC Missing Support for Integrity Check26Monitor
- Later →CVE-2021-39836Sep 29, 2021 · Adobe Acrobat Reader DC AcroForm buttonGetIcon Use-After-Free Remote Code Execution Vulnerability52Plan
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
Proof of concept available
A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.
Evidence
- Proof-of-concept repository on GitHub ×1
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Proof-of-concept repository on GitHub | stars:26 | 2021-12-02 |
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.
- Published
- First PoC+90 d
- TodayOct 29, 2026+1883 d
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 researchersFinders, 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
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system 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
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
nvd-primary
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.