new file mode 100644
@@ -0,0 +1,136 @@
+From 2798504fa2663364573cf2d1043d8d7fef389499 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Jos=C3=A9=20Padilla?= <jpadilla@users.noreply.github.com>
+Date: Thu, 10 Sep 2026 08:33:25 -0400
+Subject: [PATCH] fix: reject DER public keys as HMAC secrets
+
+CVE: CVE-2026-102271
+Upstream-Status: Backport [https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499]
+
+(cherry picked from commit 2798504fa2663364573cf2d1043d8d7fef389499)
+Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
+---
+ jwt/algorithms.py | 27 ++++++++++++++++++++++++++-
+ tests/test_algorithms.py | 39 +++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 65 insertions(+), 1 deletion(-)
+
+diff --git a/jwt/algorithms.py b/jwt/algorithms.py
+index cf6da45..432fdcf 100644
+--- a/jwt/algorithms.py
++++ b/jwt/algorithms.py
+@@ -33,6 +33,7 @@ from .utils import (
+ )
+
+ try:
++ from cryptography import x509
+ from cryptography.exceptions import InvalidSignature, UnsupportedAlgorithm
+ from cryptography.hazmat.backends import default_backend
+ from cryptography.hazmat.primitives import hashes
+@@ -72,6 +73,7 @@ try:
+ NoEncryption,
+ PrivateFormat,
+ PublicFormat,
++ load_der_public_key,
+ load_pem_private_key,
+ load_pem_public_key,
+ load_ssh_public_key,
+@@ -322,10 +324,33 @@ class HMACAlgorithm(Algorithm):
+ def __init__(self, hash_alg: HashlibHash) -> None:
+ self.hash_alg = hash_alg
+
++ @staticmethod
++ def _is_der_key(key_bytes: bytes) -> bool:
++ if not has_crypto:
++ return False
++
++ try:
++ load_der_public_key(key_bytes)
++ except (TypeError, ValueError, UnsupportedAlgorithm):
++ pass
++ else:
++ return True
++
++ try:
++ x509.load_der_x509_certificate(key_bytes)
++ except (TypeError, ValueError, UnsupportedAlgorithm):
++ return False
++ else:
++ return True
++
+ def prepare_key(self, key: str | bytes) -> bytes:
+ key_bytes = force_bytes(key)
+
+- if is_pem_format(key_bytes) or is_ssh_key(key_bytes):
++ if (
++ is_pem_format(key_bytes)
++ or is_ssh_key(key_bytes)
++ or self._is_der_key(key_bytes)
++ ):
+ raise InvalidKeyError(
+ "The specified key is an asymmetric key or x509 certificate and"
+ " should not be used as an HMAC secret."
+diff --git a/tests/test_algorithms.py b/tests/test_algorithms.py
+index 4e149a7..acaa1fe 100644
+--- a/tests/test_algorithms.py
++++ b/tests/test_algorithms.py
+@@ -12,6 +12,7 @@ from .keys import load_ec_pub_key_p_521, load_hmac_key, load_rsa_pub_key
+ from .utils import crypto_required, key_path
+
+ if has_crypto:
++ from cryptography import x509
+ from cryptography.hazmat.primitives.asymmetric.ec import (
+ EllipticCurvePrivateKey,
+ EllipticCurvePublicKey,
+@@ -28,6 +29,10 @@ if has_crypto:
+ RSAPrivateKey,
+ RSAPublicKey,
+ )
++ from cryptography.hazmat.primitives.serialization import (
++ Encoding,
++ PublicFormat,
++ )
+
+ from jwt.algorithms import ECAlgorithm, OKPAlgorithm, RSAAlgorithm, RSAPSSAlgorithm
+
+@@ -187,6 +192,40 @@ class TestAlgorithms:
+ key = algo.prepare_key('{"this": "is just a json-shaped secret"}')
+ assert key == b'{"this": "is just a json-shaped secret"}'
+
++ @crypto_required
++ @pytest.mark.parametrize(
++ "key_format_name",
++ ("SubjectPublicKeyInfo", "PKCS1"),
++ )
++ def test_hmac_prepare_key_rejects_der_public_key(
++ self, key_format_name: str
++ ) -> None:
++ algo = HMACAlgorithm(HMACAlgorithm.SHA256)
++ public_key = cast(RSAPublicKey, load_rsa_pub_key())
++ der_key = public_key.public_bytes(
++ Encoding.DER, getattr(PublicFormat, key_format_name)
++ )
++
++ with pytest.raises(InvalidKeyError, match="asymmetric key"):
++ algo.prepare_key(der_key)
++
++ @crypto_required
++ def test_hmac_prepare_key_rejects_der_certificate(self) -> None:
++ algo = HMACAlgorithm(HMACAlgorithm.SHA256)
++ with open(key_path("testkey_rsa.cer"), "rb") as certificate_file:
++ certificate = x509.load_pem_x509_certificate(certificate_file.read())
++ der_certificate = certificate.public_bytes(Encoding.DER)
++
++ with pytest.raises(InvalidKeyError, match="x509 certificate"):
++ algo.prepare_key(der_certificate)
++
++ @crypto_required
++ def test_hmac_prepare_key_accepts_non_key_binary_secret(self) -> None:
++ algo = HMACAlgorithm(HMACAlgorithm.SHA256)
++ secret = b"\x30\x82not-a-der-key"
++
++ assert algo.prepare_key(secret) == secret
++
+ @crypto_required
+ def test_rsa_should_parse_pem_public_key(self) -> None:
+ algo = RSAAlgorithm(RSAAlgorithm.SHA256)
+--
+2.35.6
@@ -15,6 +15,7 @@ SRC_URI += "file://CVE-2026-48522.patch \
file://CVE-2026-102269.patch \
file://CVE-2026-102267.patch \
file://CVE-2026-102268_CVE-2026-102270.patch \
+ file://CVE-2026-102271.patch \
"
SRC_URI[sha256sum] = "c74a7a2adf861c04d002db713dd85f84beb242228e671280bf709d765b03672b"