Published: 30 Oct 2026
Last updated: 30 Oct 2026
A vulnerability in the Brotli decompression library affects some versions of Hypercell. A remote attacker can use specially crafted Brotli-compressed data to corrupt process memory. Successful exploitation can disclose data in memory, stop a process, or potentially run unauthorized code.
On-premises customers must upgrade to a fixed version. If a fixed version is not available for your current version, apply the applicable workarounds and file a Support ticket to plan an upgrade.
Upgrade affected on-premise instances
Install the applicable fixed version as soon as possible. A workaround reduces exposure but does not remove the vulnerable library.
About the vulnerability
The vulnerability is tracked as CVE-2026-111497 and is also called HTTP2Shell. It affects the Brotli decoder when an application decompresses an attacker-controlled Brotli stream.
The CVE record assigns the vulnerability a CVSS v4.0 score of 9.2, Critical. The exposure in Hyperscience depends on the product version and how the instance receives or retrieves data.
Affected Hypercell versions
The following sections describe how the vulnerability affects each Hypercell version range.
Hypercell v42.0–v44.0
Versions v42.0–v44.0 can reach the vulnerable decoder through the following:
Processing any PDF file: An attacker does not need an account on the instance when PDF files arrive from an external source, such as email ingestion.
Responses back from Supervision task notifications: Where responses come form an URL configured by an API user.
Files retrieved through
/api/v5/flow_runs/<id>/data: This endpoint requires an authenticated user.Responses from other HTTP endpoints configured by an administrator: Such as identity providers or another instance connected to the Artifacts Repository. For example, Members of the Artifacts managers permission group could also gain access to the connected instance.
Hypercell v33.0–v41.0
Versions v33.0–v41.0 can reach the vulnerable decoder through the following HTTP responses:
Responses back from Supervision task notifications: Where responses come form an URL configured by an API user.
Responses from other HTTP endpoints configured by an administrator, such as identity providers.
PDF processing does not reach the vulnerable decoder in these versions.
Components that do not decode Brotli responses
The following components run without the affected Python Brotli package and do not decode Brotli-compressed HTTP responses:
Input Blocks and Output Blocks, including the Email, S3, and Box listeners and notifiers.
The HTTP REST Block.
Outbound requests from Custom Code Blocks and Python Code Blocks.
In v42.0–v44.0, PDF files introduced by these components remain affected when the application processes the files.
Fixed versions
Upgrade each affected instance to the applicable fixed version.
Product | Affected version line | Fixed version |
|---|---|---|
Hypercell | v44.0 | v44.0.2 |
Hypercell | v43.2 | v43.2.5 |
Hypercell | v42.3 | v42.3.19 |
Hypercell | v42.0 | v42.0.27 |
Hypercell | v41.0 | v41.0.39 |
Hypercell | v40.0 | v40.0.39 |
If your version is not listed, apply the applicable workaround and contact your Hyperscience representative. Hyperscience does not plan to patch archived versions. Your representative can help you identify a supported upgrade path.
For information about patch availability, see Patching Hyperscience and Supported Versions.
Remediation for SaaS deployments
Hyperscience deploys the fixed versions to supported SaaS instances. Customers do not need to install the patch. Hyperscience contacts customers whose instances require an upgrade outside the regular maintenance process.
Remediation for on-premises deployments
Upgrade each affected Kubernetes or Docker/Podman deployment to a fixed version from the table. If your instance requires multiple major-version upgrades, complete the upgrades sequentially.
For upgrade planning and instructions, see The Upgrade Process. Hyperscience Support provides the download link for the latest applicable patch in your Support ticket.
Workarounds
Use the workarounds that apply to your product and version until you complete the upgrade.
Hypercell v42.0–v44.0
Temporarily disable automated external ingestion channels, such as email listeners, where PDF files originate. If continuous document intake is required, route incoming files through an upstream security gateway or sandbox to scan and validate the documents.
Send Supervision task notifications only to trusted endpoints, or turn off the notifications.
Give API access only to trusted users and services. Where possible, enforce source IP allowlisting for API access to trusted network blocks.
Restrict all administrator-configured external integrations, such as Identity Providers, Artifact repositories, and outbound webhooks, exclusively to fully trusted internal infrastructure or verified domains.
Block direct outbound internet access from the application hosts via security groups or firewall egress rules.
If outbound traffic routes through an intercepting forward proxy, configure it to strip the Accept-Encoding: br header or reject inbound responses with
Content-Encoding: br.
Connect the Artifacts Repository only to trusted instances, and limit the Artifacts managers permission group to trusted users.
Hypercell v33.0–v41.0
Send Supervision task notifications only to trusted endpoints, or turn off the notifications.
Restrict all administrator-configured external integrations, such as Identity Providers, Artifact repositories, and outbound webhooks, exclusively to fully trusted internal infrastructure or verified domains.
Block direct outbound internet access from the application hosts via security groups or firewall egress rules.
If outbound traffic routes through an intercepting forward proxy, configure it to strip the Accept-Encoding: br header or reject inbound responses with
Content-Encoding: br.
If you suspect a compromise
Follow your organization's incident-response process and notify Hyperscience by filing a support ticket. Include your product version, deployment type, and the time range of the suspected activity. Reminder: Send logs or other sensitive information through our approved support channel only.
References
Revision history
Date | Change |
|---|---|
30 Oct 2026 | Initial publication. |