CISA Adds Langflow, N-central, and Tomcat to KEV as TeamCity RCE Comes Under Active Attack

Washington — CISA handed defenders two clocks this week, not one. On August 5 the agency added three actively exploited flaws — in IBM's Langflow, N-able N-central, and Apache Tomcat — to its Known Exploited Vulnerabilities (KEV) catalog, with a federal remediation deadline of August 7. Around the same time it posted a separate KEV entry for JetBrains TeamCity, where a critical remote code execution bug is now being exploited in the wild and carries its own August 8 deadline.

For anyone running these products, the story is priority, not panic. Two of the CVEs in play score CVSS 9.8 and allow unauthenticated remote code execution: Langflow's CVE-2026-9198 and TeamCity's CVE-2026-63077 — the latter confirmed under active exploitation by CISA. Those are the two to move on first, ahead of the authentication-bypass and cluster-encryption issues that round out the list. Below is what each entry actually is, a clean CVE reference table, a patch-priority stack, and a concrete verification step per product.

What CISA Added, and When

The August 5 batch bundled three unrelated products that share one trait: each is a high-value administration, application, or cluster component, and each has crossed CISA's active-exploitation threshold. Per SecurityWeek and The Hacker News, the entries break down as follows.

Langflow — CVE-2026-9198 (CVSS 9.8). A code injection flaw in Langflow, the open-source agentic-AI application platform now under IBM's stewardship, that lets an unauthenticated attacker reach full remote code execution on default deployments. The Register notes that Langflow has been targeted repeatedly through 2026, so exposure here is not theoretical. The fix shipped in July 2026 with Langflow version 1.10.1. CISA has not published exploitation specifics for this CVE, and no named victims have been confirmed — treat both as open questions rather than reported fact.

Apache Tomcat — CVE-2026-34486 (CVSS 7.5). This is the EncryptInterceptor bypass the brief flagged for ID confirmation, and the verified identifier is CVE-2026-34486. It is a missing-encryption-of-sensitive-data weakness that defeats EncryptInterceptor, the Tomcat cluster component that adds pre-shared-key encryption to messages passed between cluster nodes. The Apache Tomcat team fixed it in April 2026 in versions 11.0.21, 10.1.54, and 9.0.117. Worth noting: its CVSS is 7.5, not a 9.8 — lower severity than the RCE entries, and it only matters to deployments that actually run clustering with EncryptInterceptor configured.

N-able N-central — CVE-2026-18556 (CVSS 8.2). Here the paperwork is genuinely confusing, so it is worth being precise. The flaw added in this batch is CVE-2026-18556, an authentication bypass in N-central. As The Hacker News reported, an incomplete fix for that issue prompted N-able to ship a second patch tracked as CVE-2026-18577 (also CVSS 8.2) — the vulnerability CISA had already placed on the KEV list on August 3. That is the one The CyberSignal covered when CISA first added it, and again when the initial patch turned out to be bypassable and MSPs were told to move fast. The practical takeaway is unchanged: both CVEs are now flagged as exploited, and the single N-central update that closes them out is the one to install.

Federal Civilian Executive Branch agencies have until August 7, 2026 to remediate all three, per Binding Operational Directive 22-01. That is a firm signal to everyone else about how quickly these are being weaponized — the earlier N-central round even drew a compressed three-day federal deadline when god-mode takeovers were in progress.

TeamCity: The One Already Being Exploited

The separate KEV entry is the one that should reorder your afternoon. CVE-2026-63077 (CVSS 9.8) is a deserialization-of-untrusted-data vulnerability in on-premise JetBrains TeamCity, reachable through the agent polling protocol that build agents use to check in with the central server. An unauthenticated attacker with network access to the server can sidestep authentication checks and run arbitrary operating system commands with the privileges of the TeamCity server process.

CISA's catalog entry states it plainly: "JetBrains TeamCity contains a deserialization of untrusted data vulnerability that could allow unauthenticated remote code execution via the agent polling protocol." JetBrains disclosed the bug on July 27, 2026 and, at the time, said it had no evidence of exploitation. CISA's August 5 addition means that assumption no longer holds, even though — as SecurityWeek reported — the identity of the attackers, the method, and the scale are not yet public.

Why it stings more than a typical RCE: a compromised TeamCity server exposes stored credentials, build configurations, and server state, and can let an attacker tamper with build artifacts and downstream CI/CD pipelines. That is a foothold into everything the build system touches. JetBrains fixed it in TeamCity 2026.1.3 (build 222742) and 2025.11.7 (build 208264). The federal deadline for CVE-2026-63077 is August 8, 2026.

The Five CVEs at a Glance

My Read: Order of Operations

My read: if you own more than one of these, the sequence is not the same as the CVSS ranking. Patch TeamCity CVE-2026-63077 first — it is the only entry here with confirmed in-the-wild exploitation, it is unauthenticated RCE, and a build server sits upstream of your production software, which makes it a supply-chain problem the moment it is touched. Langflow CVE-2026-9198 is the co-priority: same 9.8, same unauthenticated RCE, and an AI platform that teams too often stand up on the open internet with default settings. The two N-central CVEs come next — 8.2 and clearly targeted, but bounded to N-central operators, and closed by a single update. Tomcat CVE-2026-34486 ranks last of the five despite being on the same list, because at CVSS 7.5 it only bites clustered deployments that have EncryptInterceptor enabled; if you do not run clustering, verify that and move on.

Verify, Don't Assume

Patching is only half the job; confirm you are actually on a fixed build. One concrete check per product:

• TeamCity: open Administration → Server Administration → Diagnostics (or the Help/About panel) and confirm the version is 2026.1.3 (build 222742) or 2025.11.7 (build 208264) or later. Separately, check whether the server and its agent-polling port are reachable from untrusted networks and restrict them.
• Langflow: run pip show langflow (or check the UI footer) and confirm the version is 1.10.1 or newer. Also verify the instance is not exposed to the internet with default or disabled authentication.
• N-able N-central: check the server version under Help → About. Hosted environments are upgraded by N-able automatically; on-premise deployments must apply the update by hand, so confirm the build rather than assuming.
• Apache Tomcat: run version.sh (or version.bat) to read the build, and confirm 11.0.21, 10.1.54, or 9.0.117 or later. Then inspect server.xml for a cluster block using EncryptInterceptor to judge whether the flaw even applies to you.

Five CVEs, two federal deadlines two days apart, and one — TeamCity — already being used against real targets. The clean version of this week: patch the two 9.8s today, roll the N-central update this week, and confirm whether Tomcat clustering even puts you in scope.

Primary Documents

• CISA — Adds Three Known Exploited Vulnerabilities to Catalog (Langflow, N-central, Tomcat)
• CISA — Adds One Known Exploited Vulnerability to Catalog (TeamCity CVE-2026-63077)
• CISA — Known Exploited Vulnerabilities Catalog
• Apache Tomcat security advisory — CVE-2026-34486 (EncryptInterceptor)
• The Register — IBM's Langflow under active attack (CVE-2026-9198)