Description
A submitted topology carries two lists of blobstore keys, dependency_jars and dependency_artifacts,
which the client fills in after uploading the corresponding blobs. Nimbus performed no validation of their
contents on the submission path, yet acts on them in two places.
During cleanup of a finished topology, Nimbus deletes the keys named in those lists, and the deletion is
performed as the Nimbus subject, for which the blobstore short-circuits its ACL check. A submitter who
listed a key belonging to another topology, such as its -stormjar.jar, could therefore cause
that blob to be deleted when their own topology was cleaned up.
Separately, on acquiring leadership a Nimbus compares the dependency keys of all active topologies against
the blobstore contents and surrenders leadership if any is missing. A single key that does not exist, on a
single active topology, therefore causes every Nimbus to acquire leadership, surrender it and requeue
indefinitely, leaving the cluster without a leader and unable to schedule, clean up or accept submissions.
Mitigation
Upgrade to 3.1.0, where a submission is refused unless every entry in both lists is a dependency blob key
and exists in the blobstore.
Note that this validates new submissions only; a topology stored by an affected version with an invalid list
is unaffected by the upgrade. An operator whose cluster is failing to retain a leader should inspect the
Nimbus log for the dependency keys reported as missing and remove or resubmit the topology naming them.
Users who cannot upgrade immediately should restrict topology submission to trusted principals.
Credit
This issue was discovered by rzo1 while investigating an unrelated blobstore defect.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it