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From 051ea341b5573fe3edcd53042f347929b92c2b92 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Padilla?= <jpadilla@webapplicate.com>
Date: Thu, 12 Mar 2026 12:46:08 -0400
Subject: [PATCH] Merge commit from fork
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Co-authored-by: José Padilla <jpadilla@users.noreply.github.com>
CVE: CVE-2026-32597
Upstream-Status: Backport [https://github.com/jpadilla/pyjwt/commit/051ea341b5573fe3edcd53042f347929b92c2b92]
Signed-off-by: Hitendra Prajapati <hprajapati@mvista.com>
---
CHANGELOG.rst | 2 +
jwt/api_jws.py | 27 +++++++++++++-
tests/test_api_jws.py | 87 +++++++++++++++++++++++++++++++++++++++++++
tests/test_api_jwt.py | 18 +++++++++
4 files changed, 132 insertions(+), 2 deletions(-)
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 8bc2319..289f45b 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -26,6 +26,8 @@ Changed
Fixed
~~~~~
+- Validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. by @dmbs335 in
+ `GHSA-752w-5fwx-jx9f <https://github.com/jpadilla/pyjwt/security/advisories/GHSA-752w-5fwx-jx9f>`__
Added
~~~~~
diff --git a/jwt/api_jws.py b/jwt/api_jws.py
index fa6708c..1750442 100644
--- a/jwt/api_jws.py
+++ b/jwt/api_jws.py
@@ -129,7 +129,7 @@ class PyJWS:
header: dict[str, Any] = {"typ": self.header_typ, "alg": algorithm_}
if headers:
- self._validate_headers(headers)
+ self._validate_headers(headers, encoding=True)
header.update(headers)
if not header["typ"]:
@@ -197,6 +197,8 @@ class PyJWS:
payload, signing_input, header, signature = self._load(jwt)
+ self._validate_headers(header)
+
if header.get("b64", True) is False:
if detached_payload is None:
raise DecodeError(
@@ -309,14 +311,35 @@ class PyJWS:
if not alg_obj.verify(signing_input, prepared_key, signature):
raise InvalidSignatureError("Signature verification failed")
- def _validate_headers(self, headers: dict[str, Any]) -> None:
+ # Extensions that PyJWT actually understands and supports
+ _supported_crit: set[str] = {"b64"}
+
+ def _validate_headers(
+ self, headers: dict[str, Any], *, encoding: bool = False
+ ) -> None:
if "kid" in headers:
self._validate_kid(headers["kid"])
+ if not encoding and "crit" in headers:
+ self._validate_crit(headers)
def _validate_kid(self, kid: Any) -> None:
if not isinstance(kid, str):
raise InvalidTokenError("Key ID header parameter must be a string")
+ def _validate_crit(self, headers: dict[str, Any]) -> None:
+ crit = headers["crit"]
+ if not isinstance(crit, list) or len(crit) == 0:
+ raise InvalidTokenError("Invalid 'crit' header: must be a non-empty list")
+ for ext in crit:
+ if not isinstance(ext, str):
+ raise InvalidTokenError("Invalid 'crit' header: values must be strings")
+ if ext not in self._supported_crit:
+ raise InvalidTokenError(f"Unsupported critical extension: {ext}")
+ if ext not in headers:
+ raise InvalidTokenError(
+ f"Critical extension '{ext}' is missing from headers"
+ )
+
_jws_global_obj = PyJWS()
encode = _jws_global_obj.encode
diff --git a/tests/test_api_jws.py b/tests/test_api_jws.py
index 3385716..434874b 100644
--- a/tests/test_api_jws.py
+++ b/tests/test_api_jws.py
@@ -815,3 +815,90 @@ class TestJWS:
)
assert len(record) == 1
assert "foo" in str(record[0].message)
+
+ def test_decode_rejects_unknown_crit_extension(
+ self, jws: PyJWS, payload: bytes
+ ) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": ["x-custom-policy"], "x-custom-policy": "require-mfa"},
+ )
+ with pytest.raises(InvalidTokenError, match="Unsupported critical extension"):
+ jws.decode(token, secret, algorithms=["HS256"])
+ def test_decode_rejects_empty_crit(self, jws: PyJWS, payload: bytes) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": []},
+ )
+ with pytest.raises(InvalidTokenError, match="must be a non-empty list"):
+ jws.decode(token, secret, algorithms=["HS256"])
+ def test_decode_rejects_non_list_crit(self, jws: PyJWS, payload: bytes) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": "b64"},
+ )
+ with pytest.raises(InvalidTokenError, match="must be a non-empty list"):
+ jws.decode(token, secret, algorithms=["HS256"])
+ def test_decode_rejects_crit_with_non_string_values(
+ self, jws: PyJWS, payload: bytes
+ ) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": [123]},
+ )
+ with pytest.raises(InvalidTokenError, match="values must be strings"):
+ jws.decode(token, secret, algorithms=["HS256"])
+ def test_decode_rejects_crit_extension_missing_from_header(
+ self, jws: PyJWS, payload: bytes
+ ) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": ["b64"]},
+ )
+ with pytest.raises(InvalidTokenError, match="missing from headers"):
+ jws.decode(token, secret, algorithms=["HS256"])
+ def test_decode_accepts_supported_crit_extension(
+ self, jws: PyJWS, payload: bytes
+ ) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": ["b64"], "b64": False},
+ is_payload_detached=True,
+ )
+ decoded = jws.decode(
+ token,
+ secret,
+ algorithms=["HS256"],
+ detached_payload=payload,
+ )
+ assert decoded == payload
+ def test_get_unverified_header_rejects_unknown_crit(
+ self, jws: PyJWS, payload: bytes
+ ) -> None:
+ secret = "secret"
+ token = jws.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": ["x-unknown"], "x-unknown": "value"},
+ )
+ with pytest.raises(InvalidTokenError, match="Unsupported critical extension"):
+ jws.get_unverified_header(token)
diff --git a/tests/test_api_jwt.py b/tests/test_api_jwt.py
index 82b9299..618b60f 100644
--- a/tests/test_api_jwt.py
+++ b/tests/test_api_jwt.py
@@ -802,3 +802,21 @@ class TestJWT:
options={"strict_aud": True},
algorithms=["HS256"],
)
+
+ # -------------------- Crit Header Tests --------------------
+
+ def test_decode_rejects_token_with_unknown_crit_extension(self, jwt: PyJWT) -> None:
+ """RFC 7515 §4.1.11: tokens with unsupported critical extensions MUST be rejected."""
+ from jwt.exceptions import InvalidTokenError
+
+ secret = "secret"
+ payload = {"sub": "attacker", "role": "admin"}
+ token = jwt.encode(
+ payload,
+ secret,
+ algorithm="HS256",
+ headers={"crit": ["x-custom-policy"], "x-custom-policy": "require-mfa"},
+ )
+
+ with pytest.raises(InvalidTokenError, match="Unsupported critical extension"):
+ jwt.decode(token, secret, algorithms=["HS256"])
--
2.50.1
|
