CVE-2025-68156

The record

Expr is an expression language and expression evaluation for Go. Prior to version 1.17.7, several builtin functions in Expr, including `flatten`, `min`, `max`, `mean`, and `median`, perform recursive traversal over user-provided data structures without enforcing a maximum recursion depth. If the evaluation environment contains deeply nested or cyclic data structures, these functions may recurse indefinitely until exceed the Go runtime stack limit. This results in a stack overflow panic, causing the host application to crash. While exploitability depends on whether an attacker can influence or inject cyclic or pathologically deep data into the evaluation environment, this behavior represents a denial-of-service (DoS) risk and affects overall library robustness. Instead of returning a recoverable evaluation error, the process may terminate unexpectedly. In affected versions, evaluation of expressions that invoke certain builtin functions on untrusted or insufficiently validated data structures can lead to a process-level crash due to stack exhaustion. This issue is most relevant in scenarios where Expr is used to evaluate expressions against externally supplied or dynamically constructed environments; cyclic references (directly or indirectly) can be introduced into arrays, maps, or structs; and there are no application-level safeguards preventing deeply nested input data. In typical use cases with controlled, acyclic data, the issue may not manifest. However, when present, the resulting panic can be used to reliably crash the application, constituting a denial of service. The issue has been fixed in the v1.17.7 versions of Expr. The patch introduces a maximum recursion depth limit for affected builtin functions. When this limit is exceeded, evaluation aborts gracefully and returns a descriptive error instead of panicking. Additionally, the maximum depth can be customized by users via `builtin.MaxDepth`, allowing applications with legitimate deep structures to raise the limit in a controlled manner. Users are strongly encouraged to upgrade to the patched release, which includes both the recursion guard and comprehensive test coverage to prevent regressions. For users who cannot immediately upgrade, some mitigations are recommended. Ensure that evaluation environments cannot contain cyclic references, validate or sanitize externally supplied data structures before passing them to Expr, and/or wrap expression evaluation with panic recovery to prevent a full process crash (as a last-resort defensive measure). These workarounds reduce risk but do not fully eliminate the issue without the patch.

Affected packages

Related vulnerabilities

• CVE-2025-4673 Proxy-Authorization and Proxy-Authenticate headers persisted on cross-origin redirects… Also affects opentelemetry-collector
• CVE-2025-22871 The net/http package improperly accepts a bare LF as a line terminator in chunked data… Also affects opentelemetry-collector
• CVE-2026-32287 Boolean XPath expressions that evaluate to true can cause an infinite loop in… Also affects amazon-cloudwatch-agent
• CVE-2026-33186 gRPC-Go is the Go language implementation of gRPC. Also affects amazon-cloudwatch-agent
• CVE-2026-27142 Actions which insert URLs into the content attribute of HTML meta tags are not escaped. Also affects amazon-cloudwatch-agent
• CVE-2026-27139 On Unix platforms, when listing the contents of a directory using File.ReadDir or… Also affects amazon-cloudwatch-agent
• CVE-2026-25679 url.Parse insufficiently validated the host/authority component and accepted some invalid… Also affects amazon-cloudwatch-agent
• CVE-2026-24051 OpenTelemetry-Go is the Go implementation of OpenTelemetry. Also affects amazon-cloudwatch-agent