Exploitation evidence
Known exploited · CISA KEV listed
Added 2021-11-03. Ransomware campaign use: Unknown.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2021-11-17. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
Adobe / Acrobat Reader
Default status: Not specified
- affected: unspecified to ≤ 2020.001.30020 (custom)
- affected: unspecified to ≤ 2021.001.20150 (custom)
- affected: unspecified to ≤ 2017.011.30194 (custom)
- affected: unspecified to ≤ None (custom)
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.52132,
"percentile": 0.98975
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.52132,
"percentile": 0.98968
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.52132,
"percentile": 0.98966
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.52132,
"percentile": 0.98966
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.52132,
"percentile": 0.98965
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.52132,
"percentile": 0.98964
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.52132,
"percentile": 0.98962
}05 Nov 2026, 18:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
"adp": [
{
"providerMetadata": {
"dateUpdated": "2024-08-03T21:47:32.615Z",
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
"shortName": "CVE"
},
"references": [
{
"tags": [
"x_transferred"
],
"url": "https://helpx.adobe.com/security/products/acrobat/apsb21-29.html"
}
],
"title": "CVE Program Container"
},
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2021-28550",
"options": [
{
"Exploitation": "active"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2025-02-04T18:17:32.968582Z",
"version": "2.0.3"
},
"type": "ssvc"
}
},
{
"other": {
"content": {
"dateAdded": "2021-11-03",
"reference": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28550"
},
"type": "kev"
}
}
],
"providerMetadata": {
"dateUpdated": "2025-10-21T23:25:35.586Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"government-resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28550"
}
],
"timeline": [
{
"lang": "en",
"time": "2021-11-03T00:00:00.000Z",
"value": "CVE-2021-28550 added to CISA KEV"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "Acrobat Reader",
"vendor": "Adobe",
"versions": [
{
"lessThanOrEqual": "2020.001.30020",
"status": "affected",
"version": "unspecified",
"versionType": "custom"
},
{
"lessThanOrEqual": "2021.001.20150",
"status": "affected",
"version": "unspecified",
"versionType": "custom"
},
{
"lessThanOrEqual": "2017.011.30194",
"status": "affected",
"version": "unspecified",
"versionType": "custom"
},
{
"lessThanOrEqual": "None",
"status": "affected",
"version": "unspecified",
"versionType": "custom"
}
]
}
],
"datePublic": "2021-05-11T00:00:00.000Z",
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_0": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.6,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H",
"version": "3.0"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-416",
"description": "Use After Free (CWE-416)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2023-03-28T00:00:00.000Z",
"orgId": "078d4453-3bcd-4900-85e6-15281da43538",
"shortName": "adobe"
},
"references": [
{
"url": "https://helpx.adobe.com/security/products/acrobat/apsb21-29.html"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution"
}
},
"cveMetadata": {
"assignerOrgId": "078d4453-3bcd-4900-85e6-15281da43538",
"assignerShortName": "adobe",
"cveId": "CVE-2021-28550",
"datePublished": "2021-09-02T16:07:20.687Z",
"dateReserved": "2021-03-16T00:00:00.000Z",
"dateUpdated": "2025-10-21T23:25:35.586Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.1"
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.52132,
"percentile": 0.98961
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.52132,
"percentile": 0.9896
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.51851,
"percentile": 0.9895
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2021-28550",
"cwes": [
"CWE-416"
],
"dateAdded": "2021-11-03",
"dueDate": "2021-11-17",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-28550",
"product": "Acrobat and Reader",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Adobe Acrobat and Reader contains a use-after-free vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.",
"vendorProject": "Adobe",
"vulnerabilityName": "Adobe Acrobat and Reader Use-After-Free Vulnerability"
}