{"id":"CVE-2021-28550","kind":"vulnerability","aliases":["CVE-2021-28550"],"related":[],"title":"Adobe Acrobat and Reader: Adobe Acrobat and Reader Use-After-Free Vulnerability","description":"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.","summary":"Adobe Acrobat and Reader contain a use-after-free memory bug that lets a crafted PDF run code as the current user. CISA lists it as actively exploited in the wild.","severity":"critical","cvss":9.6,"epss":0.51851,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Adobe Acrobat and Reader","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["adobe-acrobat","adobe-reader","desktop","exploited","macos","other","windows"],"not_affected_if":["fixed-version-installed"],"how_to_check":"Open Acrobat or Reader and check Help > About to see the installed version, then compare it to the patched release in the Adobe advisory.","fix":"Update Adobe Acrobat and Reader to the patched version named in Adobe's advisory, as CISA directs.","status":"open","published_at":"2021-09-02T17:15:08+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:32:09+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"other","confidence":0.6,"triage":{"at":"2026-10-23T21:32:09Z","model":"claude-haiku-5-5","output":{"fix":"Update Adobe Acrobat and Reader to the patched version named in Adobe's advisory, as CISA directs.\nunknown","reach":"unknown","impact":"high","summary":"Adobe Acrobat and Reader contain a use-after-free memory bug that lets a crafted PDF run code as the current user. CISA lists it as actively exploited in the wild.","category":"other","who_cares":["adobe-acrobat","adobe-reader","windows","macos","desktop"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker runs code as the logged-in user via a malicious PDF.","analyst_note":"Find the patched Acrobat/Reader version and the Adobe advisory URL for CVE-2021-28550 to fill how_to_check and fix.","how_to_check":"Open Acrobat or Reader and check Help > About to see the installed version, then compare it to the patched release in the Adobe advisory.\nunknown","needs_analyst":true,"not_affected_if":["fixed-version-installed"],"user_interaction":"yes","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000481,"input_tokens":2847,"output_tokens":392,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':15A,18A '-28550':16A,19A '2017.011.30194':79C '2020.001.30020':75C '2021.001.20150':72C 'achiev':98C 'acrobat':2A,6A,21A,26B,36B,67C 'activ':62B 'adob':1A,5A,25B,28B,35B 'adobe':20A 'adobe-acrobat':24B 'adobe-read':27B 'affect':83C 'and':22A 'arbitrari':99C 'attack':92C 'bug':46B 'cisa':58B 'code':53B,100C 'contain':39B 'context':104C 'could':93C 'craft':50B 'current':56B,107C 'cve':14A,17A 'dc':69C 'desktop':30B 'earlier':74C,77C,81C 'execut':101C 'exploit':31B,63B,109C 'file':124C 'free':12A,44B,88C 'interact':115C 'issu':112C 'let':48B 'leverag':94C 'list':59B 'maco':32B 'malici':123C 'memori':45B 'must':120C 'open':121C 'pdf':51B 'reader':4A,8A,23A,29B,38B,68C 'requir':113C 'run':52B 'unauthent':91C 'use':10A,42B,86C 'use-after-fre':9A,41B 'user':57B,108C,114C 'version':70C,71C 'victim':119C 'vulner':13A,89C,96C 'wild':66B 'window':34B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-09-02T17:15:08+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-28550","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-28550","severity":null,"published_at":"2021-11-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:53+00:00","fetched_at":"2026-10-25T12:39:25+00:00","note":null},{"source":"epss","external_id":"CVE-2021-28550","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-28550","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:44+00:00","fetched_at":"2026-10-23T19:13:44+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-28550","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-28550","severity":null,"published_at":"2021-09-02T17:15:08+00:00","modified_at":"2026-06-17T03:46:30+00:00","first_seen_at":"2026-10-23T21:57:35+00:00","fetched_at":"2026-10-23T21:57:35+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}