{"id":1627,"date":"2026-09-14T15:10:44","date_gmt":"2026-09-14T09:40:44","guid":{"rendered":"https:\/\/www.hexnode.com\/threat-watch\/?p=1627"},"modified":"2026-09-17T09:40:31","modified_gmt":"2026-09-17T04:10:31","slug":"papercut-ai-attack-395-organizations","status":"publish","type":"post","link":"https:\/\/www.hexnode.com\/threat-watch\/papercut-ai-attack-395-organizations\/","title":{"rendered":"AI-Powered PaperCut Exploitation Hits 395 Organizations"},"content":{"rendered":"

A PaperCut AI attack compromised at least 440 PaperCut NG\/MF instances across 395 identified organizations in 48 countries. GreyNoise linked the campaign to a likely Russian-speaking threat actor using hundreds of AI agents to accelerate exploit development and deployment.<\/p>\n

The campaign targeted CVE-2026-81578, an authentication bypass, and CVE-2026-82078, an unsafe dynamic class-loading vulnerability.<\/p>\n

Together, the flaws created a path from unauthorized configuration changes to unsafe dynamic class loading. That chain could lead to code execution on vulnerable PaperCut servers.<\/p>\n

PaperCut has confirmed active exploitation and released security maintenance versions 24.1.10, 25.0.13, and 26.0.5. Organizations should upgrade to an appropriate fixed release rather than relying on the earlier emergency patches.<\/p>\n

PaperCut AI Attack at a Glance<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Detail<\/span><\/b>\u00a0<\/span><\/td>\nInformation<\/span><\/b>\u00a0<\/span><\/td>\n<\/tr>\n
Affected product<\/span>\u00a0<\/span><\/td>\nPaperCut NG\/MF<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
CVEs<\/span>\u00a0<\/span><\/td>\nCVE-2026-81578, CVE-2026-82078<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
CVE-2026-81578<\/span>\u00a0<\/span><\/td>\nAuthentication bypass<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
CVSS<\/span>\u00a0<\/span><\/td>\n8.8, CVSS v4.0<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
CVE-2026-82078<\/span>\u00a0<\/span><\/td>\nUnsafe dynamic class loading<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
CVSS<\/span>\u00a0<\/span><\/td>\n9.4, CVSS v4.0<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
Confirmed exploitation<\/span>\u00a0<\/span><\/td>\nYes<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
Compromised instances<\/span>\u00a0<\/span><\/td>\nAt least 440<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
Identified\u00a0organizations<\/span>\u00a0<\/span><\/td>\n395 across 48 countries<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
Credentials harvested<\/span>\u00a0<\/span><\/td>\n280 victims, including credentials recovered through LSASS memory and registry-secret dumping<\/td>\n<\/tr>\n
OS\/domain secrets obtained<\/span>\u00a0<\/span><\/td>\n147 victims, including secrets used to support Active Directory privilege escalation<\/td>\n<\/tr>\n
Domain admin reached<\/span>\u00a0<\/span><\/td>\n12 organizations<\/span>\u00a0<\/span><\/td>\n<\/tr>\n
Fixed releases<\/span>\u00a0<\/span><\/td>\n24.1.10, 25.0.13, 26.0.5<\/span>\u00a0<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

How Two PaperCut Flaws Created a Path to Code Execution<\/h2>\n

The campaign depended on two vulnerabilities with different roles.<\/p>\n

CVE-2026-81578<\/a> affects the PaperCut NG\/MF web management interface. PaperCut describes it as an improper access-control<\/a> vulnerability. Under specific conditions, unauthenticated requests targeting administrative functions can trigger backend actions before access validation completes.<\/p>\n

As a result, a remote unauthenticated attacker can modify certain system configurations. The vulnerability carries a CVSS v4.0 score of 8.8.<\/p>\n

CVE-2026-82078<\/a> affects PaperCut’s database connection utilities. The application could instantiate database driver classes using configurable driver names without validating them against an approved allowlist.<\/p>\n

An attacker who could manipulate those configuration parameters could execute arbitrary Java bytecode already present on the application classpath. That code runs under the security context of the PaperCut server process. PaperCut rates this vulnerability 9.4 under CVSS v4.0.<\/p>\n

Chaining the two weaknesses therefore connected unauthorized administrative configuration changes with code execution in the PaperCut server process.<\/p>\n

Hundreds of AI Agents Compressed the PaperCut Attack Timeline<\/h2>\n

The distinguishing feature of this campaign was not simply that AI helped write malicious code.<\/p>\n

GreyNoise found that the adversary built a lab containing vulnerable PaperCut software and an Active Directory server. The attacker used that environment to develop and test exploitation before targeting real systems.<\/p>\n

Hundreds of AI agents then supported the operation at scale. GreyNoise reported that the infrastructure combined OpenAI’s Codex harness with a DeepSeek model. The attacker also used Netlas to generate target lists.<\/p>\n

The resulting attack tempo was unusually compressed.<\/p>\n

GreyNoise observed the adversary move from an empty workspace to remote code execution<\/a> against a real victim in under four hours. Domain administrator access followed roughly two hours later.<\/p>\n

Once the full campaign launched, at least 11 organizations were compromised within 26 seconds. In one U.S. high school environment, initial access progressed to domain administrator privileges in seven minutes.<\/p>\n

However, domain-level escalation occurred in only a subset of compromised environments.<\/p>\n

How PaperCut Compromise Reached Active Directory<\/h2>\n

GreyNoise documented three main routes from compromised PaperCut infrastructure toward domain-level privileges.<\/p>\n

First, attackers dumped LSASS memory and registry secrets from domain-joined PaperCut servers. Recovered credential hashes could then support pass-the-hash activity against domain controllers.<\/p>\n

Second, the adversary exploited noPac in environments that remained vulnerable to CVE-2021-42278 and CVE-2021-42287. Those older Active Directory vulnerabilities created another privilege-escalation route.<\/p>\n

Third, some environments exposed an even shorter path. Where PaperCut ran on a domain controller or under a domain administrator service account, the attacker could add a newly created account to the Domain Admins group.<\/p>\n

GreyNoise reported that after successfully reaching domain administrator privileges, the attacker used DCSync to replicate Active Directory credential data from domain controllers.<\/p>\n

The findings demonstrate why PaperCut’s deployment context matters. Compromise of the application can become considerably more serious when its server holds privileged credentials or operates with excessive domain permissions.<\/p>\n

How the PaperCut AI Attack Progressed Beyond Initial Access<\/h2>\n

The compromise extended well beyond initial server access. Credential harvesting occurred on 280 victims, while researchers observed operating system or domain secrets obtained from 147.<\/p>\n

However, organizations should distinguish those figures from full domain compromise. GreyNoise observed domain administrator access at 12 organizations.<\/p>\n

The campaign’s final objective also remains unclear. GreyNoise said it could not determine whether the actor planned to retain or transfer access, steal data, deploy ransomware, or pursue another objective.<\/p>\n

Therefore, the confirmed incident should not be described as a ransomware campaign or confirmed data-theft operation.<\/p>\n

PaperCut Recommends Moving to Security Maintenance Releases<\/h2>\n

PaperCut initially issued emergency patches as it investigated active exploitation. The vendor has since released full security maintenance versions that replace those emergency fixes.<\/p>\n

Organizations should upgrade to:<\/p>\n