CVE-2026-123555 (CVSS 7.5)

Description

Zebra from 2.3.0 before 7.0.0 contains a denial of service vulnerability that allows unauthenticated peers to evade misbehavior scoring by sending transactions or blocks with invalid transparent scripts. Attackers can flood mempool with script-failing transactions or serve forged v5 block bodies with altered scriptSig bytes to exhaust CPU and repeatedly stall block sync.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0043

Probability of exploitation

0.38%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-755 CWE-755

References

Other References

https://github.com/ZcashFoundation/zebra/commit/e8db87eb69254e0d4eedd058eadd48bdfa09065a https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-jq45-ghw5-v37x https://www.vulncheck.com/advisories/zebra-2.3.0-before-7.0.0-denial-of-service-via-unscored-script-verification-failures

Frequently Asked Questions

What is CVE-2026-123555? +

Zebra from 2.3.0 before 7.0.0 contains a denial of service vulnerability that allows unauthenticated peers to evade misbehavior scoring by sending transactions or blocks with invalid transparent scripts. Attackers can flood mempool with script-failing transactions or serve forged v5 block bodies with altered scriptSig bytes to exhaust CPU and repeatedly stall block sync. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-123555? +

CVE-2026-123555 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0043, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-123555? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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