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From c77d816548bd768df262ba0204904168584c0bd1 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]
Dropped changes to the changelog, version bump and tests during backport.
Signed-off-by: Ankur Tyagi <ankur.tyagi85@gmail.com>
---
jwt/api_jws.py | 27 +++++++++++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/jwt/api_jws.py b/jwt/api_jws.py
index 654ee0b..db2c80f 100644
--- a/jwt/api_jws.py
+++ b/jwt/api_jws.py
@@ -137,7 +137,7 @@ 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"]:
@@ -208,6 +208,8 @@ 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(
@@ -327,14 +329,35 @@ 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
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