Zebra zebrad before 7.0.0 Reachable Assertion DoS via Peer Disconnection
Affects zebrad 6.4.2 and earlier, and 7.0.0-rc.0, on release builds that talk to untrusted P2P peers. CVSS 8.2 is the only rating given. 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? →
- 0.31% · 23rd 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? →
- 30/100 · 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
ZcashFoundation Zebra zebrad before 7.0.0 contains a reachable assertion race condition that allows unauthenticated remote peers to abort the node by triggering disconnection during a blocked outbound send. Malicious peers can return empty FindBlocks or FindHeaders replies and stop reading their socket, dropping an unresolved MustUseClientResponseSender and terminating syncing nodes.
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
- Severity8.2/10CVSS 8.2
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 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.
Workaround: Run zebrad under a process supervisor with automatic restart to limit the outage if the process aborts.
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.
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Questions about CVE-2026-123557
Is CVE-2026-123557 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 peer disconnection can trigger a reachable assertion in zebrad. Because release builds abort the process on panic, a successful trigger terminates the whole node until it is restarted.Source: github.com
Which versions are affected by CVE-2026-123557?
zebra: before 7.0.0.Source: cve.now feed data
Am I affected, and how do I check?
Versions zebrad 6.4.2 and earlier, and 7.0.0-rc.0, are affected. The trigger applies on a release build, such as published binaries and Docker images, while the node accepts or makes P2P connections to untrusted peers, which is the default, and while it is syncing more than 1,000 blocks behind the network tip. Check the running version and whether the node is still catching up to the tip.Source: github.com
How do I fix CVE-2026-123557?
Upgrade to zebrad 7.0.0 or later, which contains the fix.Source: github.com