Summary
See attached
Workarounds
If full copies of each certificate on the existing blocklist are available, it is possible to compute their opposite-chirality signature, and then the appropriate second fingerprint to list in the blocklist.
Rotating out all CAs that have signed hosts on the blocklist will also prevent exploitation of this vulnerability.
Impact
When using P256 certificates (which is not the default configuration), it is possible to evade a blocklist entry created against the fingerprint of a certificate by using ECDSA Signature Malleability to use a copy of the certificate with a different fingerprint.
In order for this to affect a user or network, all of the following must be true:
CURVE_P256certificates are being used- There are one or more entries on the blocklist
- The certificates for those entries are signed by a trusted CA and not expired
- An attacker has a copy of the private key, and corresponding certificate, for one of those blocklist entries
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-25793? CVE-2026-25793 is a high-severity security vulnerability in github.com/slackhq/nebula (go), affecting versions >= 1.7.0, <= 1.10.2. It is fixed in 1.10.3.
- Which versions of github.com/slackhq/nebula are affected by CVE-2026-25793? github.com/slackhq/nebula (go) versions >= 1.7.0, <= 1.10.2 is affected.
- Is there a fix for CVE-2026-25793? Yes. CVE-2026-25793 is fixed in 1.10.3. Upgrade to this version or later.
- Is CVE-2026-25793 exploitable, and should I be worried? Whether CVE-2026-25793 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-25793 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-25793? Upgrade
github.com/slackhq/nebulato 1.10.3 or later.