Zebra before 7.0.0 Checkpoint Sync Denial of Service via Cancelled Verifier Rewind
Affects zebrad 6.4.2 and earlier and 7.0.0-rc.0, including the official Docker images, when checkpoint_sync is enabled and the node downloads blocks from untrusted peers. Fixed in zebrad 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 zebrad before 7.0.0 contains a denial of service vulnerability that allows a malicious peer to stall checkpoint sync by cancelling the verifier rewind after a failed commit. Attackers can serve a forged block with altered authorizing data plus a restart-triggering block, leaving the verifier rejecting honest blocks until restart.
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-2026-123558
Is CVE-2026-123558 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?
A malicious peer can stall a syncing Zebra node during checkpoint sync so that it makes no further progress until the node is restarted. The peer can repeat the stall after each restart.Source: github.com
Which versions are affected by CVE-2026-123558?
zebra: before 7.0.0.Source: cve.now feed data
Am I affected, and how do I check?
Zebrad 6.4.2 and earlier, and 7.0.0-rc.0, including the official Docker images. The issue applies when the node syncs through checkpoint ranges at NU5 heights or later, checkpoint_sync is enabled (the default), and blocks come from untrusted peers. Check the zebrad version in use and whether checkpoint_sync is enabled in the configuration.Source: github.com
How do I fix CVE-2026-123558?
Upgrade to zebrad 7.0.0 or later, which contains the fix.Source: github.com