GHSA-cfpf-hrx2-8rv6 · Severity: high · Ecosystem: go — Expr has Denial of Service via Unbounded Recursion in Builtin Functions
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.
Conclusion & alert: CVE-2025-68156 is rated Low Risk (33.7/100): CVSS High severity, with low exploitation likelihood (EPSS 0.04%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-03-21 | 0.05% | 0.04% | -0.02% |
| 2 | 2025-12-17 | — | 0.05% | — |
Full EPSS history (2 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | [email protected] |
GHSA-cfpf-hrx2-8rv6 · Severity: high · Ecosystem: go — Expr has Denial of Service via Unbounded Recursion in Builtin Functions
| vendor | priority | summary | link |
|---|---|---|---|
debian
|
unimportant | CVE-2025-68156 unimportant priority: Debian including 1 source packages (golang-github-antonmedv-expr), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. | https://security-tracker.debian.org/tracker/CVE-2025-68156 |
redhat
|
high | — | https://access.redhat.com/security/cve/CVE-2025-68156 |
suse
|
high | CVE-2025-68156 severity important: SUSE including 76 source package names (2.1.3-5.7:shim-15.8-1.1, alloy-1.12.2-150700.15.15.1, …), 118 product×package rows across 26 product lines (Container suse/manager/5.0/x86_64/server, Container suse/sl-micro/6.0/base-os-container, … (26 product lines)): Fixed 117, First Fixed 1. | https://www.suse.com/security/cve/CVE-2025-68156/ |
| URL | Tags |
|---|---|
| https://github.com/expr-lang/expr/pull/870 | Issue Tracking Patch |
| https://github.com/expr-lang/expr/security/advisories/GHSA-cfpf-hrx2-8rv6 | Mitigation Patch Vendor Advisory |