Two vulnerabilities, one deadline
The Cybersecurity and Infrastructure Security Agency added two vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog on May 21, 2026, citing evidence of active exploitation for both. Federal civilian agencies have until June 4 to remediate under Binding Operational Directive 22-01. The advisory covers unrelated products, an open-source AI workflow platform and an enterprise endpoint security suite, which is itself notable: attackers are working across very different parts of the stack in the same window.
CVE-2025-34291: Langflow account takeover chain
Langflow is an open-source platform for building AI agent workflows. According to the GitHub Security Advisory (GHSA-577h-p2hh-v4mv) and a technical writeup from Obsidian Security, versions up to and including 1.6.9 chain three separate weaknesses into a single exploit: an overly permissive CORS configuration on the token-refresh endpoint, a refresh-token cookie set with SameSite=None, and no CSRF protection on that endpoint. Together, they let an attacker take over a victim's account and execute arbitrary code just by getting them to visit an attacker-controlled page in a browser that already holds an authenticated Langflow session. No stolen credentials are required.
The flaw carries a CVSS v4.0 score of 9.4. The fix is version 1.7.0, which restricts CORS to trusted origins, sets the refresh-token cookie to SameSite=Strict with the Secure attribute, and adds CSRF protection to the refresh endpoint.
CVE-2026-34926: Trend Micro Apex One directory traversal
Trend Micro disclosed and patched CVE-2026-34926 in its on-premise Apex One endpoint protection product on May 21, per the company's own May 2026 security bulletin (KA-0023430). The flaw is a directory traversal issue, rated 6.7 on CVSS v3.1, medium severity. Trend Micro's bulletin describes it as exploitable by an attacker who already holds admin credentials to modify a key table on the server, which is then used to inject malicious code for deployment to connected agents. It affects on-premise server and agent builds below build 17079.
Trend Micro's fix ships as Apex One SP1 Critical Patch Build 18012 and baseline build 17079, along with updated agent packages. The vulnerability does not affect Apex One as a Service or Vision One.
What organizations need to do
Both CVEs are now formally listed as actively exploited, which is CISA's bar for KEV inclusion, not a theoretical risk rating. Federal agencies are required to patch by June 4; every other organization running either product should treat that same date as the working deadline. For Langflow, that means upgrading to 1.7.0 and auditing existing sessions for signs of prior compromise, since the exploit chain leaves limited forensic trace on the client side. For Apex One on-premise deployments, it means applying the May 21 patch builds and reviewing admin account hygiene, since the attack path assumes an attacker already has admin-level access to the management console.
Sources: CISA: Adds Two Known Exploited Vulnerabilities to Catalog · Trend Micro: Apex One and Vision One SEP May 2026 Security Bulletin (KA-0023430) · GitHub Advisory Database: GHSA-577h-p2hh-v4mv (CVE-2025-34291) · Obsidian Security: CVE-2025-34291 Analysis · Help Net Security: Actively exploited Trend Micro Apex One flaw gets CISA warning