CVE-2026-104424 Zebra before 6.1.0 Incorrect Block Size Calculation in getblocktemplate
Attackers can cause denial of service by forcing Zcash miners to produce oversized blocks due to incorrect size calculations in the block template selector.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-104424?
CVE-2026-104424 is a medium-severity vulnerability in ZcashFoundation zebra, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Zebra before 6.1.0 contains an incorrect calculation vulnerability in its ZIP-317 block template selector that omits header and transaction-count size from the block budget. Attackers can place valid selectable transactions in a victim miner's mempool to shape templates into oversized blocks, causing rejection and wasted proof-of-work.
Weakness: CWE-131
Which versions are affected by CVE-2026-104424?
How do I fix CVE-2026-104424?
No fix has been published for CVE-2026-104424 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-104424 being exploited?
There is no known exploitation of CVE-2026-104424 in the wild and no public exploit code.
Sources
Also known as GHSA-3xx8-299f-8q53, GHSA-95m2-vx53-v2jw.