How severe is CVE-2026-55236?

CVE-2026-55236 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-55236?

CVE-2026-55236 affects the following packages: langgraph-api (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-55236?

Update langgraph-api to 0.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55236 is resolved across your whole dependency graph.

How do I detect CVE-2026-55236 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for langgraph-api. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-55236 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-55236?

O3 pinpoints whether CVE-2026-55236 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-55236 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55236 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-55236 published, and has it been updated?

CVE-2026-55236 was published on August 19, 2026 and was last updated on August 19, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2026-55236

MEDIUM

CVE-2026-55236 is a medium-severity (CVSS 5.9) vulnerability in langgraph-api. O3 Security confirms whether CVE-2026-55236 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

langgraph-api: Incomplete assistant authorization in LangGraph Server run creation

Published

Aug 19, 2026

Updated

Aug 19, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Aug 19, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐍langgraph-api

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

In affected versions of langgraph-api (the LangGraph Server runtime), the run-creation path authorized the assistant attached to a run using a different authorization event than the rest of the assistant-handling code paths. Direct assistant reads and cron creation dispatch the assistants.read authorization event; run creation dispatched assistants.search with an incomplete value. In deployments whose custom authorization handlers register only an assistants.read handler (without an assistants.search handler and without a global fallback handler), no handler was consulted on the run-creation path, the returned filter set was empty, and the owner constraint was omitted from the resulting query.

As a result, in those deployments a request to create a run could reference a private assistant owned by another user, even where direct assistant reads, assistant search, and cron creation against that assistant were correctly denied. The run-creation response merged the referenced assistant's metadata, config, and context into fields returned to the requesting user. These fields can carry sensitive configuration; the runtime encrypts them at rest for that reason.

We have no evidence of this behavior occurring in the wild.

Affected users / systems

You may be affected if you:

run langgraph-api (the LangGraph Server / Agent Server runtime, including via the LangGraph Platform Helm chart), and
use custom authorization handlers that gate assistant access through an assistants.read or assistants.search handler rather than a global handler covering all assistant events.

Deployments without custom authorization handlers, or whose handlers apply an equivalent owner filter across all assistant events (for example through a global handler), are not affected.

Impact

Confidentiality: exposure of another user's private assistant metadata, config, and context through the run-creation response. These fields can contain sensitive configuration.
Integrity: creation of a run associated with another user's private assistant, beyond the requesting user's authorization scope; the run is then carried out using that assistant's configuration.

Patches / mitigation

Run creation, and the parallel cron-creation path, now dispatch the assistants.read authorization event in both the in-memory and gRPC/Postgres runtimes, matching direct assistant reads. Client-supplied run and cron metadata is no longer forwarded into that authorization event, so handlers receive a consistent value shape and determine access by returning an owner filter that is applied server-side. Fixed in langgraph-api 0.10.0.

This is a behavioral change for deployments with custom authorization handlers:

Handlers that gated assistant access only through assistants.search during run creation are no longer consulted on that path; provide an equivalent assistants.read handler that returns the same owner filter.
The metadata field on the assistants.read event during run and cron creation is no longer populated; handlers that read or stamped it should move that logic into the run/cron create handlers.

Operational guidance

Register an assistants.read handler (or a global handler covering it) that returns an owner-style filter, and confirm parity across the assistant read, search, and run/cron creation paths.
Upgrade to a release containing this change.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`langgraph-api`	all versions	0.10.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for langgraph-api. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update langgraph-api to 0.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55236 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55236 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-55236. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary In affected versions of `langgraph-api` (the LangGraph Server runtime), the run-creation path authorized the assistant attached to a run using a different authorization event than the rest of the assistant-handling code paths. Direct assistant reads and cron creation dispatch the `assistants.read` authorization event; run creation dispatched `assistants.search` with an incomplete value. In deployments whose custom authorization handlers register only an `assistants.read` handler (without an `assistants.search` handler and without a global fallback handler), no handler was consulted

O3 Security · Impact-Aware SCA

Is CVE-2026-55236 in your dependencies?

O3 detects CVE-2026-55236 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works