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Fencer Intel
medium —

GHSA-4rmq-mc2c-r495 json

Babylon Incorrect FP inactive accounting in costaking creates “phantom stake” that earns rewards after BTC unbond

published 11mo ago modified 8mo ago also GO-2025-4214

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
—
no score, EPSS covers CVEs only
public exploits
0
none known

Summary

### Summary

A state consistency bug in `x/costaking` can leave a BTC delegator with non-zero `ActiveSatoshis` (Phatom Stake) even after they have fully unbonded their BTC delegation, if their Finality Provider (FP) drops out of the active set in the exact same babylon block height. This creates a “phantom stake”: the delegator’s BTC capital is withdrawn, the FP is inactive, but costaking continues to treat the delegation as active BTC stake allowing ongoing rewards accrual without backing BTC.

### Impact

An address can keep earning costaking rewards with zero BTC staked.

Reported by @BottyBott.

Patch / fix

  • go github.com/babylonlabs-io/babylon/v4 4.2.0

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Affected packages

ecosystem package affected fixed in
go github.com/babylonlabs-io/babylon/v4
<4.2.0
4.2.0
go github.com/babylonlabs-io/babylon/v3
<=3.0.0-snapshot.250805a
all versions
 no fix listed
go github.com/babylonlabs-io/babylon/v2
<=2.3.2
all versions
 no fix listed
go github.com/babylonlabs-io/babylon
<=1.1.0
all versions
 no fix listed

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.