From f8d837b1dc1e83b0db0573fcdbb60c7f3a3d7fa6 Mon Sep 17 00:00:00 2001
From: "advisory-database[bot]"
 <45398580+advisory-database[bot]@users.noreply.github.com>
Date: Fri, 16 May 2025 14:11:57 +0000
Subject: [PATCH] Publish GHSA-qhr6-mgqr-mchm

---
 .../GHSA-qhr6-mgqr-mchm.json                  | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 advisories/github-reviewed/2025/05/GHSA-qhr6-mgqr-mchm/GHSA-qhr6-mgqr-mchm.json

diff --git a/advisories/github-reviewed/2025/05/GHSA-qhr6-mgqr-mchm/GHSA-qhr6-mgqr-mchm.json b/advisories/github-reviewed/2025/05/GHSA-qhr6-mgqr-mchm/GHSA-qhr6-mgqr-mchm.json
new file mode 100644
index 00000000000..4b1e700a397
--- /dev/null
+++ b/advisories/github-reviewed/2025/05/GHSA-qhr6-mgqr-mchm/GHSA-qhr6-mgqr-mchm.json
@@ -0,0 +1,69 @@
+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-qhr6-mgqr-mchm",
+  "modified": "2025-05-16T14:10:25Z",
+  "published": "2025-05-16T14:10:25Z",
+  "aliases": [
+    "CVE-2025-47285"
+  ],
+  "summary": "Vyper's `concat()` builtin may elide side-effects for zero-length arguments",
+  "details": "### Impact\n`concat()` may skip evaluation of side effects when the length of an argument is zero. this is due to a fastpath in the implementation which skips evaluation of argument expressions when their length is zero:\nhttps://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L560-L562\n\nin practice, it would be very unusual in user code to construct zero-length bytestrings using an expression with side-effects, since zero-length bytestrings are typically constructed with the empty literal `b\"\"`; the only way to construct an empty bytestring which has side effects would be with the ternary operator introduced in v0.3.8, e.g. `b\"\" if self.do_some_side_effect() else b\"\"`.\n\nthe following example demonstrates how the issue would look in user code\n```vyper\ncounter: public(uint256)\n\n@external\ndef test() -> Bytes[256]:\n    a: Bytes[256] = concat(b\"\" if self.sideeffect() else b\"\", b\"aaaa\")\n    return a\n\ndef sideeffect() -> bool:\n    self.counter += 1\n    return True\n```\n\nthe severity assigned is low, since, as mentioned, this would be a very unusual pattern in user-code.\n\n### Patches\n\nfix is tracked in https://github.com/vyperlang/vyper/pull/4644\n\n### Workarounds\ndon't have side effects in expressions which construct zero-length bytestrings.\n\n### References\n_Are there any links users can visit to find out more?_",
+  "severity": [
+    {
+      "type": "CVSS_V4",
+      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "PyPI",
+        "name": "vyper"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "last_affected": "0.4.2rc1"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-qhr6-mgqr-mchm"
+    },
+    {
+      "type": "ADVISORY",
+      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-47285"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/vyperlang/vyper/pull/4644"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/vyperlang/vyper"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L560-L562"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-691"
+    ],
+    "severity": "LOW",
+    "github_reviewed": true,
+    "github_reviewed_at": "2025-05-16T14:10:25Z",
+    "nvd_published_at": "2025-05-15T18:15:38Z"
+  }
+}
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