meta-openembedded/meta-python/recipes-devtools/python/files/CVE-2026-48525.patch

From e6152fb27dd439bf4541aab9b26a93134c48135f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Padilla?= <jpadilla@users.noreply.github.com>
Date: Thu, 21 May 2026 14:11:10 -0400
Subject: [PATCH] Bundle security fixes and hardening into 2.13.0
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Security:
- `HMACAlgorithm.prepare_key` rejects JWK JSON documents passed as raw
  HMAC secrets to close an algorithm-confusion gap not covered by the
  existing PEM/SSH guard. Reported by @aradona91 in GHSA-xgmm-8j9v-c9wx.
- Bind the JWT header `alg` to `PyJWK.algorithm_name` during verification
  so the caller's `algorithms` allow-list cannot be bypassed when decoding
  with a `PyJWK` / `PyJWKClient` key. Reported by @sushi-gif in
  GHSA-jq35-7prp-9v3f.
- Skip the unconditional base64 decode of the compact-form payload
  segment when `b64=false` is set, and require that segment to be empty
  (RFC 7515 Appendix F detached form). Closes an unauthenticated DoS
  amplifier. Reported by @thesmartshadow in GHSA-w7vc-732c-9m39.
- `PyJWKClient` rejects any URI whose scheme is not `http` or `https` so
  attacker-influenced URIs cannot read local files or reach unintended
  schemes via urllib's default `file://` / `ftp://` / `data:` handlers.
  Reported by @KEIJOT in GHSA-993g-76c3-p5m4.
- Preserve the cached JWK Set on fetch errors in `PyJWKClient.fetch_data`.
  The previous `finally`-block `put(None)` pattern cleared the cache on
  any transient outage. Reported by @eddieran in GHSA-fhv5-28vv-h8m8.

Fixes:
- Reject empty HMAC keys outright in `HMACAlgorithm.prepare_key` with
  `InvalidKeyError` instead of accepting them with only a warning.
  Hardening prompted by reports from @SnailSploit and @spartan8806.
- Forward per-call `options` (including `enforce_minimum_key_length`)
  from `PyJWT.decode` through to `PyJWS._verify_signature`. Thanks to
  @WLUB.
- RFC 7797 §3 compliance for `b64=false`: encoder auto-adds `"b64"` to
  `crit`; decoder rejects tokens that set `b64=false` without listing
  it in `crit`. Thanks to @MachineLearning-Nerd.

CVE: CVE-2026-48525
Upstream-Status: Backport [https://github.com/jpadilla/pyjwt/commit/95791b1759b8aa4f2203575d344d5c78564cdc81]

Backport Changes:
- Split out the b64=false payload-decoding DoS fix because the upstream
  commit bundles multiple CVEs.
- Omitted CHANGELOG.rst because it conflicted and is release documentation.
- Carried the focused
  `test_decode_b64_false_rejects_non_empty_payload_segment` regression test.
  Omitted other tests/test_api_jws.py hunks for unrelated bundled fixes.
- Omitted the 2.13.0 version bump and other bundled fixes; applicable CVE
  fixes are carried in separate patches.

(cherry picked from commit 95791b1759b8aa4f2203575d344d5c78564cdc81)
Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
---
 jwt/api_jws.py        | 22 ++++++++++++++++++----
 tests/test_api_jws.py | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/jwt/api_jws.py b/jwt/api_jws.py
index 91d2ae3..5a91bce 100644
--- a/jwt/api_jws.py
+++ b/jwt/api_jws.py
@@ -317,10 +317,24 @@ class PyJWS:
         if not isinstance(header, dict):
             raise DecodeError("Invalid header string: must be a json object")
 
-        try:
-            payload = base64url_decode(payload_segment)
-        except (TypeError, binascii.Error) as err:
-            raise DecodeError("Invalid payload padding") from err
+        if header.get("b64", True) is False:
+            # Detached payload form (RFC 7515 Appendix F): the compact-form
+            # payload segment must be empty; the caller supplies the actual
+            # payload via the `detached_payload` argument in decode_complete.
+            # Skipping the base64 decode here removes an unauthenticated work
+            # amplifier — otherwise an attacker can inflate the unused
+            # segment to force CPU + memory cost before the signature is
+            # even checked.
+            if payload_segment:
+                raise DecodeError(
+                    "Payload segment must be empty when 'b64' is false."
+                )
+            payload = b""
+        else:
+            try:
+                payload = base64url_decode(payload_segment)
+            except (TypeError, binascii.Error) as err:
+                raise DecodeError("Invalid payload padding") from err
 
         try:
             signature = base64url_decode(crypto_segment)
diff --git a/tests/test_api_jws.py b/tests/test_api_jws.py
index 0715b9e..01de813 100644
--- a/tests/test_api_jws.py
+++ b/tests/test_api_jws.py
@@ -12,7 +12,7 @@ from jwt.exceptions import (
     InvalidSignatureError,
     InvalidTokenError,
 )
-from jwt.utils import base64url_decode
+from jwt.utils import base64url_decode, base64url_encode
 from jwt.warnings import RemovedInPyjwt3Warning
 
 from .utils import crypto_required, key_path, no_crypto_required
@@ -984,6 +984,40 @@ class TestJWS:
         assert "b64" not in msg_header_obj
         assert msg_payload
 
+    def test_decode_b64_false_rejects_non_empty_payload_segment(
+        self, jws: PyJWS, payload: bytes
+    ) -> None:
+        # RFC 7515 Appendix F detached form: when b64=false, the compact-
+        # serialization payload segment must be empty. PyJWT must reject a
+        # non-empty middle segment without doing any base64-decoding work
+        # on it — that decode used to be the unauthenticated DoS amplifier.
+        secret = "secret"
+        import hmac as _hmac
+        import hashlib as _hashlib
+
+        header_obj = {
+            "typ": "JWT",
+            "alg": "HS256",
+            "b64": False,
+            "crit": ["b64"],
+        }
+        header_b64 = base64url_encode(
+            json.dumps(header_obj, separators=(",", ":")).encode()
+        )
+        # Stuff the middle segment with arbitrary attacker-controlled bytes.
+        # This should be rejected without being base64-decoded.
+        attacker_segment = b"A" * 1024
+        signing_input = b".".join([header_b64, payload])
+        sig = _hmac.new(secret.encode(), signing_input, _hashlib.sha256).digest()
+        token = b".".join(
+            [header_b64, attacker_segment, base64url_encode(sig)]
+        ).decode()
+
+        with pytest.raises(DecodeError, match="Payload segment must be empty"):
+            jws.decode(
+                token, secret, algorithms=["HS256"], detached_payload=payload
+            )
+
     def test_decode_detached_content_without_proper_argument(self, jws: PyJWS) -> None:
         example_jws = (
             "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiIsImI2NCI6ZmFsc2V9"