Brotli decoder vulnerability (CVE-2026-111497): CISO Assistant fixed in v4.1.5

SaaS customers have nothing to do: we keep your instance up to date. Self-hosted customers should upgrade to v4.1.5. The rest of this post explains the flaw, how it reached CISO Assistant, and what to do if you cannot upgrade right away.

On October 20, 2026, the Node.js project shipped fixes for CVE-2026-111497, a memory-safety flaw in Google’s Brotli decompression library, and the fixed Python bindings followed on October 22. Brotli is a widely used compression format, and its decoder is built into Node.js, Python packages and many Linux distributions. CISO Assistant used affected versions. Version 4.1.4, released on October 24, fixed every exploitable path we found. Version 4.1.5 also updates a system copy of the library that no CISO Assistant feature uses but that container scanners report.

What is CVE-2026-111497?

The Brotli decoder, versions 1.0.3 to 1.2.0, can write outside its memory buffer when it decompresses a specially crafted stream. Depending on the context, an attacker who can send such a stream could crash the process, read memory contents, or possibly run code. Some researchers call it “Node2Shell”. It is rated 9.2 (CVSS v4.0). Proofs of concept are public, but we are not aware of any exploitation in the wild at the time of writing.

How CISO Assistant was exposed

We reviewed every place where CISO Assistant decompresses Brotli data:

• Backend outgoing connections. The backend’s HTTP clients accept Brotli-compressed responses. An attacker would have needed to control the server the backend connects to. For webhooks and integrations, configuring that server requires administrator rights. When the workflows feature is enabled (it is off by default), domain managers can also configure HTTP actions in workflows. The vulnerability catalog feeds are fixed public sources reached over HTTPS. Fixed in v4.1.4 (Python brotli 1.2.1).
• Document PDF export. Users who can edit documents (analysts, domain managers and administrators) can include styling in a document, including a web font. When the document is exported to PDF, the backend decodes that font with the same Python library. Fixed in v4.1.4 (Python brotli 1.2.1).
• Frontend runtime. The frontend runs on Node.js, which bundles Brotli. Its server side only talks to our own backend, which does not send Brotli-compressed data. Fixed in v4.1.4 (Node.js 24.22.1).

What you need to do

• SaaS customers: nothing. We keep your instance up to date.
• Self-hosted customers (Community and Pro on-premises): upgrade to v4.1.5 using the usual upgrade procedure.

If you cannot upgrade right away

On v4.1.4: the paths above are already fixed. Upgrading to v4.1.5 removes the container scanner finding described below, so it can wait for your next maintenance window.

On v4.1.3 or earlier: every path above is open, but each one needs either a CISO Assistant account with elevated rights or control of a server the backend talks to. An anonymous visitor cannot reach the vulnerable code. Until you upgrade:

1. Review who holds the analyst, domain manager and administrator roles. These are the roles that can edit documents or configure outgoing connections. Remove accounts that no longer need them, and enforce multi-factor authentication.
2. Check your outgoing connections. Make sure webhooks, integrations and workflow HTTP actions point only to servers you trust. If you do not use workflows, leave the feature disabled.
3. Restrict the backend’s network egress to the hosts it actually needs (your mail server, integrations and the public catalog feeds). This blocks the outgoing-connection path even if a target is misconfigured.
4. Be careful with PDF exports of documents edited by people you do not fully trust.

There is no action needed on the frontend: we found no way for an attacker to reach its Brotli decoder.

A note for container scanners

On v4.1.4, tools such as Trivy or Grype report libbrotli1 (CVE-2026-111497) in the backend image. This is a system copy of the library, linked by the font engine. No CISO Assistant feature passes compressed data to it: web fonts in PDF exports are decoded by the Python library first. Debian published a fixed package on October 23 (DSA-6582-1), and our hardened base image’s repository carries a rebuild of it, but its version number sorts below an older, unpatched build, so a normal rebuild kept installing the unpatched one. v4.1.5 installs the fixed build explicitly, so scanners should no longer report it.

The Node.js update in v4.1.4 also fixes the other Node.js vulnerabilities disclosed in the same security release, including three rated High that affect TLS certificate checks and DNS.

References

• CVE-2026-111497 (CVE record)
• GitHub advisory for the Python bindings (GHSA-9v8h-qqgm-4m35)
• Node.js October 2026 security releases
• Debian security tracker
• Debian security advisory DSA-6582-1
• CISO Assistant v4.1.4 release
• CISO Assistant v4.1.5 release

If you have questions about your CISO Assistant deployment, contact us.