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Expr has Denial of Service via Unbounded Recursion in Builtin Functions

Type: advisorySources: OSV

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

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2025-68156
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 19:55 UTC · Revision 1

Source evidence

Expr has Denial of Service via Unbounded Recursion in Builtin Functions

core-osv · Original source

Published 16 Dec 2025, 18:24 UTC

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

osv:CVE-2025-68156
Complete source record
{
  "id": "d1af77661102b6d47356097518cc9b63b9c3f8cb36931f131333cf807dc2d004",
  "url": "https://osv.dev/vulnerability/CVE-2025-68156",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Expr has Denial of Service via Unbounded Recursion in Builtin Functions",
    "summary": "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",
    "evidence": "osv:CVE-2025-68156",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-68156",
      "aliases": [
        "CVE-2025-68156",
        "GHSA-cfpf-hrx2-8rv6",
        "GO-2025-4245"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/expr-lang/expr",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "d4722867d2df8480c650afa169b350a03d0b668a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.17.7"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "cpe": "cpe:2.3:a:expr-lang:expr:*:*:*:*:*:go:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.17.7"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
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            "v1.17.5",
            "v1.17.4",
            "v1.17.3",
            "v1.17.2",
            "v1.17.1",
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            "v1.14.0",
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            "v0.0.5",
            "v0.0.4",
            "v0.0.3",
            "v0.0.2",
            "v0.0.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-68156.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.510902830Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68156.json",
        "https://github.com/expr-lang/expr/security/advisories/GHSA-cfpf-hrx2-8rv6",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-68156",
        "https://github.com/expr-lang/expr/pull/870"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68156.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-68156",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 520265,
  "published_at": "2025-12-16T18:24:11.648+00:00"
}