diff --git a/relenv/build/darwin.py b/relenv/build/darwin.py
index 228ac22f..9f164575 100644
--- a/relenv/build/darwin.py
+++ b/relenv/build/darwin.py
@@ -25,6 +25,7 @@
     builds,
     finalize,
     get_dependency_version,
+    patch_file,
     update_sbom_checksums,
 )
 
@@ -150,6 +151,19 @@ def build_python(env: MutableMapping[str, str], dirs: Dirs, logfp: IO[str]) -> N
     # Update bundled expat to latest version
     update_expat(dirs, env)
 
+    # CPython 3.14.10 shipped a bad backport of gh-149816 (upstream PR #160006)
+    # that dropped the "!" from `int fips = !disable_fips_property(py_ht);` in
+    # Modules/_hashopenssl.c. The inverted polarity makes openssl_md5(
+    # usedforsecurity=False) fail under FIPS, so hashlib falls back to the
+    # builtin MD5 and silently bypasses FIPS enforcement. Idempotent: the
+    # correctly-fixed source has "!disable_fips_property" which this regex
+    # does not match. Remove once a CPython 3.14 point release ships the fix.
+    patch_file(
+        dirs.source / "Modules" / "_hashopenssl.c",
+        r"int fips = disable_fips_property\(",
+        "int fips = !disable_fips_property(",
+    )
+
     env["LDFLAGS"] = "-Wl,-rpath,{prefix}/lib {ldflags}".format(prefix=dirs.prefix, ldflags=env["LDFLAGS"])
     runcmd(
         [
diff --git a/relenv/build/linux.py b/relenv/build/linux.py
index 775b8326..729c451d 100644
--- a/relenv/build/linux.py
+++ b/relenv/build/linux.py
@@ -28,6 +28,7 @@
     builds,
     finalize,
     get_dependency_version,
+    patch_file,
     update_sbom_checksums,
 )
 
@@ -507,6 +508,19 @@ def build_python(env: EnvMapping, dirs: Dirs, logfp: IO[str]) -> None:
     # Update bundled expat to latest version
     update_expat(dirs, env)
 
+    # CPython 3.14.10 shipped a bad backport of gh-149816 (upstream PR #160006)
+    # that dropped the "!" from `int fips = !disable_fips_property(py_ht);` in
+    # Modules/_hashopenssl.c. The inverted polarity makes openssl_md5(
+    # usedforsecurity=False) fail under FIPS, so hashlib falls back to the
+    # builtin MD5 and silently bypasses FIPS enforcement. Idempotent: the
+    # correctly-fixed source has "!disable_fips_property" which this regex
+    # does not match. Remove once a CPython 3.14 point release ships the fix.
+    patch_file(
+        dirs.source / "Modules" / "_hashopenssl.c",
+        r"int fips = disable_fips_property\(",
+        "int fips = !disable_fips_property(",
+    )
+
     ldflagopt = f"-Wl,--rpath={dirs.prefix}/lib"
     if ldflagopt not in env["LDFLAGS"]:
         env["LDFLAGS"] = f"{ldflagopt} {env['LDFLAGS']}"
diff --git a/relenv/build/windows.py b/relenv/build/windows.py
index 317c11e0..44af4b8b 100644
--- a/relenv/build/windows.py
+++ b/relenv/build/windows.py
@@ -1007,6 +1007,19 @@ def build_python(env: EnvMapping, dirs: Dirs, logfp: IO[str]) -> None:
 
     patch_ssl_for_cpython_104135(dirs.source)
 
+    # CPython 3.14.10 shipped a bad backport of gh-149816 (upstream PR #160006)
+    # that dropped the "!" from `int fips = !disable_fips_property(py_ht);` in
+    # Modules/_hashopenssl.c. The inverted polarity makes openssl_md5(
+    # usedforsecurity=False) fail under FIPS, so hashlib falls back to the
+    # builtin MD5 and silently bypasses FIPS enforcement. Idempotent: the
+    # correctly-fixed source has "!disable_fips_property" which this regex
+    # does not match. Remove once a CPython 3.14 point release ships the fix.
+    patch_file(
+        dirs.source / "Modules" / "_hashopenssl.c",
+        r"int fips = disable_fips_property\(",
+        "int fips = !disable_fips_property(",
+    )
+
     arch_to_plat = {"amd64": "x64", "x86": "win32", "arm64": "arm64"}
     arch = env["RELENV_HOST_ARCH"]
     plat = arch_to_plat[arch]