@@ -197,7 +197,7 @@ def build_python(env: MutableMapping[str, str], dirs: Dirs, logfp: IO[str]) -> N
     xz_checksum = xz_info["sha256"]
 else:
     xz_version = "5.8.1"
-    xz_url = "http://tukaani.org/xz/xz-{version}.tar.gz"
+    xz_url = "https://github.com/tukaani-project/xz/releases/download/v{version}/xz-{version}.tar.gz"
     xz_checksum = "ed4d5589c4cfe84e1697bd02a9954b76af336931"
 
 build.add(
 
@@ -689,7 +689,7 @@ def build_python(env: EnvMapping, dirs: Dirs, logfp: IO[str]) -> None:
 else:
     # Fallback to hardcoded values
     xz_version = "5.8.1"
-    xz_url = "http://tukaani.org/xz/xz-{version}.tar.gz"
+    xz_url = "https://github.com/tukaani-project/xz/releases/download/v{version}/xz-{version}.tar.gz"
     xz_checksum = "ed4d5589c4cfe84e1697bd02a9954b76af336931"
 
 build.add(
 
@@ -367,7 +367,7 @@
   },
   "xz": {
    "5.8.2": {
-    "url": "http://tukaani.org/xz/xz-{version}.tar.gz",
+    "url": "https://github.com/tukaani-project/xz/releases/download/v{version}/xz-{version}.tar.gz",
     "sha256": "ce09c50a5962786b83e5da389c90dd2c15ecd0980a258dd01f70f9e7ce58a8f1",
     "platforms": [
      "linux",
@@ -376,7 +376,7 @@
     ]
    },
    "5.8.3": {
-    "url": "http://tukaani.org/xz/xz-{version}.tar.gz",
+    "url": "https://github.com/tukaani-project/xz/releases/download/v{version}/xz-{version}.tar.gz",
     "sha256": "3d3a1b973af218114f4f889bbaa2f4c037deaae0c8e815eec381c3d546b974a0",
     "platforms": [
      "linux",
 
@@ -331,16 +331,36 @@ def detect_sqlite_versions() -> list[tuple[str, str]]:
 
 def detect_xz_versions() -> list[str]:
     """
-    Detect available XZ versions from tukaani.org.
+    Detect available XZ versions from the tukaani-project GitHub releases API.
+
+    Sourcing xz version metadata from tukaani.org is discouraged after
+    CVE-2024-3094 (the March 2024 xz-utils supply-chain backdoor). Both
+    release tarball hosting and the authoritative release listing moved
+    to https://github.com/tukaani-project/xz, so we consult that project's
+    Releases API and skip drafts / prereleases.
     """
-    url = "https://tukaani.org/xz/"
+    url = "https://api.github.com/repos/tukaani-project/xz/releases"
     content = fetch_url_content(url)
-    # Find xz-X.Y.Z.tar.gz
-    pattern = r"xz-(\d+\.\d+\.\d+)\.tar\.gz"
-    matches = re.findall(pattern, content)
-    # Deduplicate and sort
-    versions = sorted(set(matches), key=lambda v: [int(x) for x in v.split(".")], reverse=True)
-    return versions
+    try:
+        releases = json.loads(content)
+    except json.JSONDecodeError:
+        return []
+    versions: list[str] = []
+    for release in releases:
+        if not isinstance(release, dict):
+            continue
+        if release.get("draft") or release.get("prerelease"):
+            continue
+        tag = release.get("tag_name", "")
+        if not isinstance(tag, str):
+            continue
+        # Tags are like "v5.8.4"; accept plain "5.8.4" too for robustness.
+        if tag.startswith("v"):
+            tag = tag[1:]
+        if not re.fullmatch(r"\d+\.\d+\.\d+", tag):
+            continue
+        versions.append(tag)
+    return sorted(set(versions), key=lambda v: [int(x) for x in v.split(".")], reverse=True)
 
 
 def detect_libffi_versions() -> list[str]:
@@ -691,13 +711,16 @@ def update_dependency_versions(path: pathlib.Path, deps_to_update: list[str] | N
             if "xz" not in dependencies:
                 dependencies["xz"] = {}
             if latest not in dependencies["xz"]:
-                url = f"http://tukaani.org/xz/xz-{latest}.tar.gz"
+                url = (
+                    f"https://github.com/tukaani-project/xz/releases/download/"
+                    f"v{latest}/xz-{latest}.tar.gz"
+                )
                 print(f"Downloading {url}...")
                 download_path = download_url(url, cwd)
                 checksum = sha256_digest(download_path)
                 print(f"SHA-256: {checksum}")
                 dependencies["xz"][latest] = {
-                    "url": "http://tukaani.org/xz/xz-{version}.tar.gz",
+                    "url": "https://github.com/tukaani-project/xz/releases/download/v{version}/xz-{version}.tar.gz",
                     "sha256": checksum,
                     "platforms": ["linux", "darwin", "win32"],
                 }
 
@@ -170,24 +170,37 @@ def fake_fetch(url: str) -> str:
 
 
 def test_detect_xz_versions(monkeypatch: pytest.MonkeyPatch) -> None:
-    """Test XZ version detection from tukaani.org."""
-    mock_html = """
-    <html>
-    <a href="xz-5.8.1.tar.gz">xz-5.8.1.tar.gz</a>
-    <a href="xz-5.8.0.tar.gz">xz-5.8.0.tar.gz</a>
-    <a href="xz-5.6.3.tar.gz">xz-5.6.3.tar.gz</a>
-    </html>
-    """
+    """Test XZ version detection from the tukaani-project GitHub releases API."""
+    import json
+
+    mock_releases = json.dumps(
+        [
+            {"tag_name": "v5.8.1", "draft": False, "prerelease": False},
+            {"tag_name": "v5.7.2beta", "draft": False, "prerelease": True},
+            {"tag_name": "v5.8.0", "draft": False, "prerelease": False},
+            {"tag_name": "v5.6.3", "draft": False, "prerelease": False},
+            {"tag_name": "v5.9.0-draft", "draft": True, "prerelease": False},
+        ]
+    )
+
+    captured_url: dict[str, str] = {}
 
     def fake_fetch(url: str) -> str:
-        return mock_html
+        captured_url["url"] = url
+        return mock_releases
 
     monkeypatch.setattr(pyversions, "fetch_url_content", fake_fetch)
     versions = pyversions.detect_xz_versions()
+    assert captured_url["url"] == (
+        "https://api.github.com/repos/tukaani-project/xz/releases"
+    )
     assert isinstance(versions, list)
     assert "5.8.1" in versions
     assert "5.8.0" in versions
     assert "5.6.3" in versions
+    # Draft and prerelease tags must be skipped
+    assert "5.7.2beta" not in versions
+    assert not any(v.startswith("5.9") for v in versions)
     # Verify sorting (latest first)
     assert versions[0] == "5.8.1"