CVE-2025-58189: Go stdlib - ALPN Negotiation Error Exposes Attacker Controlled Information
Summary
CVE-2025-58189: ALPN negotiation error contains attacker controlled information in crypto/tls. Affects stdlib across 2 version ranges.
< 1.24.8
>= 1.25.0, < 1.25.2
Fixed in 1.24.8 or 1.25.2, depending on the release line you run. How to fix ↓
Also tracked for
The same CVE-2025-58189 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
The Go standard library (stdlib) provides essential packages for building applications in the Go programming language. It includes various functionalities such as networking, cryptography, and data manipulation. The 'crypto/tls' package specifically handles Transport Layer Security (TLS) connections, ensuring secure communication over networks. However, it is susceptible to a vulnerability during the Application-Layer Protocol Negotiation (ALPN) process, which can expose sensitive information.
Vulnerability Detail
The vulnerability arises when the Conn.Handshake method fails during ALPN negotiation. In such cases, the error message generated contains information controlled by the attacker, specifically the ALPN protocols sent by the client. This unescaped information can potentially be exploited to gain insights into the client's behavior or to facilitate further attacks, compromising the security of the TLS connection.
How To Fix
Latest published version: go1.25.5 as of 22 Oct 2026
go get stdlib@vgo1.25.5Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 1.24.81.24.8go get stdlib@v1.24.8 -
>= 1.25.0, < 1.25.21.25.2go get stdlib@v1.25.2
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
As a temporary workaround, developers can implement additional error handling to sanitize or limit the information returned during the handshake failure. This can be done by wrapping the handshake function and controlling the output of error messages.
Conclusion
CVE-2025-58189 is a significant vulnerability in the Go standard library's TLS implementation that exposes attacker-controlled information during ALPN negotiation failures. Users are strongly advised to update to the latest patched versions to ensure the security of their applications.
See every vulnerability recorded for stdlib →
FAQ
The impact includes potential exposure of sensitive information controlled by the attacker, which could lead to further exploitation of the application.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which allows you to monitor for open-source vulnerabilities without needing to sign up.
Versions prior to 1.24.8 and 1.25.0 (up to 1.25.1) are affected by this vulnerability.
While updating is the best solution, implementing stricter error handling can help mitigate the risk temporarily.
The vulnerability was credited to the National Cyber Security Centre Finland.
References
Related vulnerabilities
Recent vulnerabilities recorded for stdlib.
