Summary
Denial of Service attack on windows app using Netty
An unsafe reading of environment file could potentially cause a denial of service in Netty.
When loaded on an Windows application, Netty attemps to load a file that does not exist. If an attacker creates such a large file, the Netty application crash.
Details
A similar issue was previously reported in https://github.com/netty/netty/security/advisories/GHSA-xq3w-v528-46rv
This issue was fixed, but the fix was incomplete in that null-bytes were not counted against the input limit.
PoC
The PoC is the same as for https://github.com/netty/netty/security/advisories/GHSA-xq3w-v528-46rv with the detail that the file should only contain null-bytes; 0x00.
When the null-bytes are encountered by the InputStreamReader, it will issue replacement characters in its charset decoding, which will fill up the line-buffer in the BufferedReader.readLine(), because the replacement character is not a line-break character.
Impact
Impact is the same as https://github.com/netty/netty/security/advisories/GHSA-xq3w-v528-46rv
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2025-25193 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.1.118.Final); upgrading removes the vulnerable code path.
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.
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Frequently Asked Questions
- What is CVE-2025-25193? CVE-2025-25193 is a medium-severity uncontrolled resource consumption vulnerability in io.netty:netty-common (maven), affecting versions < 4.1.118.Final. It is fixed in 4.1.118.Final. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2025-25193? CVE-2025-25193 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of io.netty:netty-common are affected by CVE-2025-25193? io.netty:netty-common (maven) versions < 4.1.118.Final is affected.
- Is there a fix for CVE-2025-25193? Yes. CVE-2025-25193 is fixed in 4.1.118.Final. Upgrade to this version or later.
- Is CVE-2025-25193 exploitable, and should I be worried? Whether CVE-2025-25193 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-2025-25193 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-2025-25193? Upgrade
io.netty:netty-commonto 4.1.118.Final or later.