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GHSA-2gf8-q9rr-jq3h
No affected components available
Am I affected
You are affected if:
- You run
zebradup to and includingv4.4.1. - Your node participates in a network where chain forks occur (mainnet, testnet, or any network with multiple miners).
All default configurations are affected. The corruption persists across restarts because it is written to RocksDB.
Summary
When pop_tip removes the tip block during a chain fork, stale Sapling and Orchard note commitment subtree root data is retained in the in-memory non-finalized state. When the chain subsequently finalizes, this stale data is written to the persistent RocksDB state. The corrupted subtree root history affects z_getsubtreesbyindex (used by lightwalletd for wallet synchronization) and could affect future chain verification that depends on correct subtree roots.
Details
The non-finalized state provides two methods for removing blocks: pop_root (removes the oldest block during finalization) and pop_tip (removes the newest block during a fork revert). pop_root correctly cleans up note commitment subtree contributions. pop_tip does not: it removes the block but retains the block's subtree root contributions in the in-memory state.
When a chain fork occurs and pop_tip reverts the old tip, the winning fork's chain is extended. When that chain is later finalized, the stale subtree data from the reverted blocks is included in the RocksDB write batch and persisted to disk.
The pop_root/pop_tip asymmetry is specific to subtree root handling. Other state managed by pop_tip (nullifiers, UTXOs, anchors, block hashes) uses different cleanup patterns that are not affected.
Patches
zebra-state 7.0.0 and zebrad 4.5.0.
The fix adds subtree root cleanup to pop_tip matching the pattern already used by pop_root.
Workarounds
There is no configuration-level workaround. Chain forks are natural events on any Proof-of-Work network. Operators can mitigate the downstream impact by periodically verifying subtree root consistency using z_getsubtreesbyindex against a known-good reference.
Impact
Persistent corruption of Sapling and Orchard subtree root history in the RocksDB state database. The corruption survives node restarts. Downstream consumers that rely on z_getsubtreesbyindex for wallet synchronization (primarily lightwalletd and light wallets) receive incorrect subtree roots. This does not directly affect consensus validation of new blocks but can cause wallet synchronization failures or incorrect wallet state. Recovery requires rebuilding the state database from scratch.
Credit
Reported by @dingledropper via a private GitHub Security Advisory submission.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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