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A GitHub-reviewed security advisory, not necessarily under active exploitation the way our CISA KEV advisories are, but a real, disclosed vulnerability in an open-source dependency.
Affected packages
Vulnerable: < 0.95.3
Patched in 0.95.3
Details
The V1 DurableTask stream handler registers worker-supplied durable task external IDs in an in-memory callback routing map before verifying that the authenticated tenant owns the task. If the tenant-scoped ownership check fails, the handler logs the error and continues, but the map entry persists until the stream closes.
Durable callback delivery resolves the destination stream by task_external_id only, without checking tenant identity. As a result, a tenant A worker that knows a tenant B durable task external UUID can hold its stream open and receive tenant B's durable callback result payload when the callback is delivered on the same dispatcher process.
This advisory requires an attacker to successfully guess a durable task external UUID belonging to another tenant. Durable task external IDs are generated with uuid.New() (UUIDv4) and are not enumerable across tenants, so exploitation requires prior knowledge of a target task UUID through an out-of-band channel. Thus, while the following environments are impacted, there is an extremely low probability it would be exploited.
Who is impacted. Any Hatchet deployment that hosts more than one tenant on the same instance:
Single-tenant self-hosted deployments are unaffected in practice (the "victim" and "attacker" tenants would be the same).
EPSS, exploit probability
Low0.24%
estimated chance of real-world exploitation in the next 30 days, higher than 15.6% of every CVE FIRST.org scores
Refreshed 11/7/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.
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