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fix(python-ecdsa): CVE-2026-33936 #2

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8 changes: 8 additions & 0 deletions debian/changelog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,11 @@
python-ecdsa (0.19.0-2+deepin1) UNRELEASED; urgency=medium

* Non-maintainer upload.
* Fix CVE-2026-33936: reject truncated DER lengths in
octet/constructed functions

-- OpenClaw Security Agent <security@openclaw.ai> Mon, 27 Apr 2026 15:10:08 +0800

python-ecdsa (0.19.0-2) unstable; urgency=medium

* Team upload.
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44 changes: 44 additions & 0 deletions debian/patches/CVE-2026-33936.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
Index: github-python-ecdsa-CVE-2026-33936/src/ecdsa/der.py
===================================================================
--- github-python-ecdsa-CVE-2026-33936.orig/src/ecdsa/der.py
+++ github-python-ecdsa-CVE-2026-33936/src/ecdsa/der.py
@@ -138,6 +138,8 @@ def remove_constructed(string):
)
tag = s0 & 0x1F
length, llen = read_length(string[1:])
+ if length > len(string) - 1 - llen:
+ raise UnexpectedDER("Length longer than the provided buffer")
body = string[1 + llen : 1 + llen + length]
rest = string[1 + llen + length :]
return tag, body, rest
@@ -161,6 +163,8 @@ def remove_octet_string(string):
n = str_idx_as_int(string, 0)
raise UnexpectedDER("wanted type 'octetstring' (0x04), got 0x%02x" % n)
length, llen = read_length(string[1:])
+ if length > len(string) - 1 - llen:
+ raise UnexpectedDER("Length longer than the provided buffer")
body = string[1 + llen : 1 + llen + length]
rest = string[1 + llen + length :]
return body, rest
Index: github-python-ecdsa-CVE-2026-33936/src/ecdsa/test_der.py
===================================================================
--- github-python-ecdsa-CVE-2026-33936.orig/src/ecdsa/test_der.py
+++ github-python-ecdsa-CVE-2026-33936/src/ecdsa/test_der.py
@@ -476,3 +476,17 @@ def test_oids(ids):
decoded_oid, rest = remove_object(encoded_oid)
assert rest == b""
assert decoded_oid == ids
+
+def test_remove_octet_string_rejects_truncated_length():
+ # OCTET STRING: declared length 4096, but only 3 bytes present
+ bad = b"\x04\x82\x10\x00" + b"ABC"
+ with pytest.raises(UnexpectedDER, match="Length longer than the provided buffer"):
+ remove_octet_string(bad)
+
+def test_remove_constructed_rejects_truncated_length():
+ # Constructed tag: 0xA0 (context-specific constructed, tag=0)
+ # declared length 4096, but only 3 bytes present
+ bad = b"\xA0\x82\x10\x00" + b"ABC"
+ with pytest.raises(UnexpectedDER, match="Length longer than the provided buffer"):
+ remove_constructed(bad)
+
1 change: 1 addition & 0 deletions debian/patches/series
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Original file line number Diff line number Diff line change
@@ -1,2 +1,3 @@
00-remove-temp-test-dir.patch
remove-six.patch
CVE-2026-33936.patch
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