Zebra before 7.0.0 Denial of Service via Quadratic Sighash Computation
Zebrad releases before 7.0.0 run with the default configuration are affected when the node accepts peer connections or relays transactions and is synced near the tip. Fixed in 7.0.0.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 7.0.0
- Who is exposed
- Default setups
Do first: Check every install: default setups are affected.
- Last modified
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.34% · 28th percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 31/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Default setups
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Zebra before 7.0.0 contains an inefficient algorithmic complexity vulnerability that allows unauthenticated peers to exhaust verification threads by submitting transactions with many transparent inputs. Attackers can relay invalid transactions with tens of thousands of inputs, forcing quadratic ZIP-244 or ZIP-243 digest recomputation that stalls Rayon-backed block verification for minutes.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure22/25Default setups, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 71 if added to CISA KEV
- Would score about 66 if CISA's SSVC rates exploitation active
What to do
Check every install: default setups are affected.
Upgrade to a fixed version: 7.0.0.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- ZcashFoundation zebra
fixed in 7.0.0
Evidence 2
- Advisory
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123559
Is CVE-2026-123559 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
Zebra spends excessive CPU time on transaction signature hashing, which grows quadratically, so a peer can make a node spend minutes of CPU per transaction. This stalls block verification, can leave a mining node unable to verify new blocks, and can make its block templates go stale.Source: github.com
Which versions are affected by CVE-2026-123559?
zebra: before 7.0.0.Source: cve.now feed data
Am I affected, and how do I check?
Zebrad releases before 7.0.0 with the default configuration. The node must accept inbound peer connections or relay transactions from peers (the default), or expose sendrawtransaction to untrusted callers, and must be synced close to the tip so the mempool is enabled. To check, look at the zebrad version and at these connection and RPC settings.Source: github.com
How do I fix CVE-2026-123559?
Upgrade to zebrad 7.0.0 or later, which contains the fix. The facts list no workaround.Source: github.com