{"id":"CVE-2026-85880","kind":"vulnerability","aliases":["CVE-2026-85880"],"related":[],"title":"Heap-based buffer overflow in Windows ALPC allows an authorized attacker to elevate privileges locally","description":"Microsoft Windows Advanced Local Procedure Call contains a heap-based buffer overflow vulnerability that allows an attacker to elevate privileges locally.\n\nCISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","summary":"Heap-based buffer overflow in Windows ALPC. Code running in a low-privilege AppContainer can escape the sandbox and gain SYSTEM locally, with no user interaction. Microsoft reports exploitation detected; it is not publicly disclosed. Fixed in the Sep 8 2026 updates. CVSS 7.8.","severity":"high","cvss":7.8,"epss":null,"exploited":true,"exploited_at":"2026-09-08T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"Windows 10 22H2/21H2","fixed":["10.0.19045.7725"],"affected":">= 10.0.19044.0, < 10.0.19045.7725","ecosystem":"vendor"},{"name":"Windows 10 1607 / Windows Server 2016","fixed":["10.0.14393.9512"],"affected":">= 10.0.14393.0, < 10.0.14393.9512","ecosystem":"vendor"},{"name":"Windows 10 1809 / Windows Server 2019","fixed":["10.0.17763.9245"],"affected":">= 10.0.17763.0, < 10.0.17763.9245","ecosystem":"vendor"},{"name":"Windows Server 2012 R2","fixed":["6.3.9600.23398"],"affected":"< 6.3.9600.23398","ecosystem":"vendor"},{"name":"Windows Server 2012","fixed":["6.2.9200.26349"],"affected":"< 6.2.9200.26349","ecosystem":"vendor"},{"name":"microsoft windows 10 1607","fixed":["10.0.14393.9512"],"affected":"< 10.0.14393.9512","ecosystem":"vendor"},{"name":"microsoft windows 10 1809","fixed":["10.0.17763.9245"],"affected":"< 10.0.17763.9245","ecosystem":"vendor"},{"name":"microsoft windows 10 21h2","fixed":["10.0.19044.7725"],"affected":"< 10.0.19044.7725","ecosystem":"vendor"},{"name":"microsoft windows 10 22h2","fixed":["10.0.19045.7725"],"affected":"< 10.0.19045.7725","ecosystem":"vendor"},{"name":"microsoft windows server 2012","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"microsoft windows server 2012","fixed":[],"affected":"= r2","ecosystem":"vendor"},{"name":"microsoft windows server 2016","fixed":["10.0.14393.9512"],"affected":"< 10.0.14393.9512","ecosystem":"vendor"},{"name":"microsoft windows server 2019","fixed":["10.0.17763.9245"],"affected":"< 10.0.17763.9245","ecosystem":"vendor"},{"name":"microsoft windows server 2022","fixed":["10.0.20348.5622"],"affected":"< 10.0.20348.5622","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","local","microsoft-windows","privilege-escalation","sandbox-escape","self-hosted","vendor","windows"],"not_affected_if":["non-windows-systems","patched-sep-2026"],"how_to_check":"Run winver, or in PowerShell: [System.Environment]::OSVersion.Version. Compare the full build number with the fixed build, e.g. Win10 22H2 10.0.19045.7725, Server 2016/Win10 1607 10.0.14393.9512, Server 2012 R2 6.3.9600.23398, Server 2012 6.2.9200.26349. Or check that the Sep 2026 cumulative update is installed: Get-HotFix -Id KB5122878 (Win10 21H2/22H2), KB5122876 (1809), KB5123099 (2016/1607), KB5123066 (2012 R2), KB5123065 (2012), KB5122882 (Server 2022).","fix":"Install the Sep 8 2026 Windows cumulative or monthly rollup update. KBs: KB5122878 (Win10 21H2/22H2), KB5122876 (Win10 1809 and Server 2019), KB5123099 (Server 2016 and Win10 1607), KB5123066 (Server 2012 R2), KB5123065 (Server 2012), KB5122882 (Server 2022). No workaround was found. CISA required action: apply the update under BOD 26-04 and the forensics triage requirements.","status":"resolved","published_at":"2026-09-08T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:31:39+00:00","updated_at":"2026-10-23T23:44:52+00:00","category":"vendor","confidence":0.8,"triage":{"at":"2026-10-23T20:31:39Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update for CVE-2026-85880 per vendor instructions; the sources do not name the patched build. Follow CISA BOD 26-04 guidance for cloud-hosted Windows systems, or discontinue use where mitigations are unavailable.","summary":"A heap-based buffer overflow in the Windows Advanced Local Procedure Call (ALPC) component lets a local user corrupt memory and elevate privileges. CISA lists it as actively exploited in the wild.","category":"vendor","who_cares":["windows","microsoft-windows","self-hosted"],"confidence":0.6,"analyst_note":"Find the Microsoft advisory for CVE-2026-85880 to get affected builds, patched KB numbers and any mitigation; the CISA KEV entry only gives the required action.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["non-windows-systems"],"severity_if_unknown":"high"},"cost_usd":0.000387,"input_tokens":2200,"output_tokens":333,"severity_before":"unknown"},"analyst_status":"done","analyst_note":"Find the Microsoft advisory for CVE-2026-85880 to get affected builds, patched KB numbers and any mitigation; the CISA KEV entry only gives the required action.","search":"'-04':184C,210C,241C '-2026':18A,21A '-85880':19A,22A '10':26A,29A,35A,49A,53A,57A,61A '1607':30A,50A '1809':36A,54A '2012':42A,46A,66A,70A '2016':33A,74A '2019':39A,78A '2022':82A '2026':141B '21h2':58A '22h2':62A '22h2/21h2':27A '26':183C,209C,240C '7.8':144B '8':140B 'accord':173C 'action':169C 'adher':237C 'advanc':147C 'allow':9A,160C 'alpc':8A,106B 'appcontain':114B 'appli':170C 'applic':207C 'asset':231C 'attack':12A,162C 'author':11A 'base':3A,101B,155C,188C 'bod':182C,208C,239C 'buffer':4A,102B,156C 'call':150C 'cisa':167C,180C,197C 'cloud':213C 'code':107B 'complianc':178C 'contain':151C 'cve':17A,20A 'cvss':143B 'detect':130B 'disclos':135B 'discontinu':216C 'elev':14A,164C 'ensur':177C,236C 'escal':90B 'escap':93B,116B 'evalu':229C 'exploit':83B,129B 'exposur':234C 'fix':136B 'follow':206C 'forens':199C 'gain':120B 'guidanc':195C,211C 'guidelin':243C 'heap':2A,100B,154C 'heap-bas':1A,99B,153C 'host':96B 'instruct':176C 'interact':126B 'internet':233C 'local':16A,84B,122B,148C,166C 'low':112B 'low-privileg':111B 'microsoft':23A,47A,51A,55A,59A,63A,67A,71A,75A,79A,86B,127B,145C 'microsoft-window':85B 'mitig':171C,222C 'note':194C,205C 'overflow':5A,103B,157C 'patch':242C 'priorit':185C 'privileg':15A,89B,113B,165C 'privilege-escal':88B 'procedur':149C 'product':220C 'public':134B 'r2':43A 'report':128B 'requir':168C,201C 'respons':227C 'risk':190C 'run':108B 'sandbox':92B,118B 'sandbox-escap':91B 'secur':186C 'see':191C,202C 'self':95B 'self-host':94B 'sep':139B 'server':32A,38A,41A,45A,65A,69A,73A,77A,81A 'servic':214C 'stakehold':225C 'system':121B 'triag':200C 'unavail':224C 'updat':142B,187C 'url':192C,203C 'use':217C 'user':125B 'vendor':97B,175C 'vulner':158C 'window':7A,87B,98B,105B,146C 'windows':24A,25A,28A,31A,34A,37A,40A,44A,48A,52A,56A,60A,64A,68A,72A,76A,80A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-09-08T00:00:00+00:00","kev":{"dateAdded":"2026-09-08","dueDate":"2026-09-22","requiredAction":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2026-85880","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-85880","severity":null,"published_at":"2026-09-08T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T15:39:39+00:00","note":null},{"source":"analyst","external_id":"CVE-2026-85880:123","url":null,"severity":null,"published_at":"2026-10-23T21:39:11+00:00","modified_at":"2026-10-23T21:39:11+00:00","first_seen_at":"2026-10-23T21:39:11+00:00","fetched_at":"2026-10-23T21:39:11+00:00","note":"MSRC advisory (Sep 8 2026) read: ALPC heap overflow, AppContainer escape to SYSTEM, exploitation detected, not publicly disclosed. Builds from CVE record; KBs from Rapid7 (secondary). Win11 and 2019 fixed builds not read. No PoC link found; social search not done."},{"source":"nvd","external_id":"CVE-2026-85880","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-85880","severity":null,"published_at":"2026-09-08T18:21:14+00:00","modified_at":"2026-09-24T23:19:20+00:00","first_seen_at":"2026-10-23T23:44:52+00:00","fetched_at":"2026-10-23T23:44:52+00:00","note":null}],"documents":[{"id":1162,"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85880","title":"MSRC: Windows ALPC Elevation of Privilege (CVE-2026-85880)","kind":"advisory","source":"analyst","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":null},{"id":1163,"url":"https://www.rapid7.com/db/vulnerabilities/cve-2026-85880/","title":"Rapid7 DB: CVE-2026-85880 (KB list)","kind":"other","source":"analyst","text":null,"published_at":null,"relation":"fix","confidence":null,"note":null},{"id":1164,"url":"https://www.cve.org/CVERecord?id=CVE-2026-85880","title":"CVE record CVE-2026-85880 (affected builds)","kind":"other","source":"analyst","text":null,"published_at":null,"relation":"describes","confidence":null,"note":null}],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}