Day-after follow-up to our April 18 coverage: Shadowserver has published telemetry showing 6,400+ Apache ActiveMQ servers exposed online are still vulnerable to CVE-2026-34197, the 13-year-old code injection flaw CISA added to KEV last week with an April 30 federal patch deadline. Geographic breakdown: Asia leads with 2,925 vulnerable servers, North America follows at 1,409, Europe at 1,334. Horizon3's Naveen Sunkavally (who discovered the flaw using the Claude AI assistant as his research tool) is urging admins to treat this as high priority, noting ActiveMQ has been a repeated target for real-world attackers - CVE-2016-3088 and CVE-2023-46604 are both on KEV, with the latter used as a zero-day by the TellYouThePass ransomware gang. The Apache maintainers patched the flaw on March 30 in ActiveMQ Classic 6.2.3 and 5.19.4. Horizon3 recommends searching broker logs for suspicious connections using the internal VM transport protocol with the brokerConfig=xbean:http:// query parameter as an indicator of exploitation.
CISA added eight actively-exploited vulnerabilities to its Known Exploited Vulnerabilities catalog on April 20, with federal agencies required to patch three Cisco Catalyst SD-WAN Manager flaws by today, April 23, and the remaining five by May 4. The Cisco trio (CVE-2026-20122, CVE-2026-20128, CVE-2026-20133) enable arbitrary file upload with vmanage user privileges, recovery of stored credentials for the DCA user, and unauthenticated disclosure of sensitive configuration data. Cisco confirmed exploitation of the first two in March 2026. The other five cover a wide blast radius: CVE-2025-32975 is a CVSS 10.0 authentication bypass in Quest KACE Systems Management Appliance letting attackers impersonate any user without credentials, exploited in the wild by unknown actors last month per Arctic Wolf. CVE-2023-27351 is the PaperCut NG/MF bypass that Microsoft's Lace Tempest chained into Cl0p and LockBit deployments back in 2023. CVE-2024-27199 is a path traversal in JetBrains TeamCity giving limited admin actions - its sibling CVE-2024-27198 is already on the KEV list. CVE-2025-48700 is a Zimbra XSS that the Ukrainian CERT attributes to UAC-0233/UAC-0250 for stealing mailbox contents, MFA backup codes, and application passwords. CVE-2025-2749 is a Kentico Xperience Staging Sync Server path traversal.
A critical code injection flaw in Apache ActiveMQ Classic has been under active exploitation in the wild, and CISA added it to the Known Exploited Vulnerabilities catalog on April 16 with a federal patch deadline of April 30. The flaw, tracked as CVE-2026-34197 (CVSS 8.8), has been 'hiding in plain sight' for 13 years according to Horizon3.ai researcher Naveen Sunkavally. The vulnerability is in the Jolokia JMX-HTTP bridge exposed at /api/jolokia/. An attacker can send crafted HTTP requests with a malicious discovery URI that forces the broker to load a remote Spring XML configuration. Because Spring initializes beans before validation, attackers execute arbitrary OS commands via Runtime.exec() - effectively turning a messaging broker into a remote command runner. Fortinet FortiGuard Labs telemetry shows exploitation attempts peaking on April 14, 2026. SAFE Security reports threat actors actively scanning for exposed Jolokia management endpoints.
A CVSS 9.8 authentication bypass in nginx-ui, the popular open-source web management interface for Nginx servers, is being actively exploited in the wild. The flaw, codenamed MCPwn by Pluto Security, exists because the /mcp_message endpoint added for Model Context Protocol (AI integration) support only checks IP whitelisting - and the default whitelist is empty, meaning it allows all connections. One unauthenticated HTTP POST request lets an attacker invoke all MCP tools: rewrite Nginx config files, reload the server, intercept all traffic, and harvest admin credentials. Attackers chain it with CVE-2026-27944 (exposed encryption keys via the backup API) to extract the node_secret needed for full MCP access. Recorded Future flagged active exploitation and assigned a risk score of 94/100. Shodan shows 2,600 publicly exposed instances, mostly in China, the US, Indonesia, and Germany. Pluto Security's key lesson: AI integration endpoints expose the same capabilities as the core application but often skip its security controls.
Just days after Microsoft patched BlueHammer (CVE-2026-33825) in Tuesday's Patch Tuesday, the same researcher 'Chaotic Eclipse' (aka Nightmare-Eclipse) has released a second Microsoft Defender local privilege escalation zero-day called RedSun. The exploit works on fully-patched Windows 10, Windows 11, and Windows Server systems with Windows Defender enabled, even after installing this week's April updates. The flaw abuses Defender's cloud file rollback behavior: when Defender detects a file with a 'cloud tag' it tries to restore it to its original location without validating the target path. The exploit uses NTFS junctions and opportunistic locks to redirect the write to C:\Windows\System32, overwriting system files like TieringEngineService.exe to gain SYSTEM privileges. Huntress Labs is reporting all three recently-leaked Windows Defender zero-days (BlueHammer, RedSun, and UnDefend) are now being exploited in the wild. The researcher has threatened to drop more severe RCE exploits in protest of how Microsoft handled their disclosure process. No patch available for RedSun yet. Working PoC code is public on GitHub.
Adobe has released an emergency security update (APSB26-43, priority-1) to patch CVE-2026-34621, the Adobe Reader zero-day we reported on April 10 that had been exploited since December 2025 via malicious PDF documents. The flaw has now been classified as a prototype pollution vulnerability leading to arbitrary code execution - more severe than the initial fingerprinting and data theft we described. Adobe confirmed it's worse than just information leakage: the underlying bug can achieve full RCE, not just the reconnaissance stage observed in early exploitation. CVSS was initially scored 9.6 but Adobe revised it down to 8.6 after changing the attack vector from Network to Local. EXPMON researcher Haifei Li, who first disclosed the flaw, was credited by Adobe. All users on Windows and macOS should update immediately - Adobe assigned this patch its highest priority rating.
An unpatched zero-day in Adobe Acrobat Reader has been actively exploited since at least November 2025 using booby-trapped PDF documents. The exploit, discovered by EXPMON researcher Haifei Li, works on the latest version of Adobe Reader without any user interaction beyond opening the file. It abuses privileged Acrobat JavaScript APIs (util.readFileIntoStream and RSS.addFeed) to silently harvest local files, OS details, language settings, and the Reader version from the victim's machine, then sends everything to an attacker-controlled server. The PDFs use Russian-language lures related to the oil and gas industry. The attack is a two-stage operation: the first pass fingerprints the target, and if the system meets the attacker's criteria, a follow-on RCE or sandbox escape payload is delivered. Only 5 out of 64 antivirus engines on VirusTotal detected the sample. No CVE has been assigned and no patch is available.
If you patched FortiClient EMS for CVE-2026-21643 two weeks ago by upgrading to 7.4.5, you're now vulnerable to a new zero-day. CVE-2026-35616 is a CVSS 9.1 pre-authentication API access bypass affecting versions 7.4.5 and 7.4.6 - the exact versions customers upgraded to. Defused Cyber spotted exploitation in the wild starting March 31. Fortinet released an emergency weekend hotfix on Saturday, with watchTowr noting attackers deliberately timed this for the Easter holiday when security teams are at half strength.
Cisco Talos uncovered a large-scale automated campaign by threat cluster UAT-10608 that exploits React2Shell - a CVSS 10.0 pre-auth RCE flaw in React Server Components used by Next.js. One crafted HTTP request is all it takes to get code execution, no credentials needed. The attackers scan with Shodan and Censys, breach Next.js apps, then deploy the NEXUS Listener framework to harvest database credentials, SSH keys, AWS tokens, Stripe API keys, Kubernetes secrets, and GitHub tokens at scale. At least 766 hosts across multiple cloud providers were compromised within 24 hours.
Google pushed an emergency Chrome update to fix a use-after-free bug in Dawn, the engine behind Chrome's WebGPU graphics standard. CVE-2026-5281 is already being exploited - an attacker who has compromised the browser's renderer process can use a crafted HTML page to execute arbitrary code, potentially escaping Chrome's sandbox. This is the fourth actively exploited Chrome zero-day in 2026, and the third targeting graphics or rendering subsystems. CISA added it to the KEV catalog with an April 15 deadline.
TrustStrike Labs