EUVD-2026-43738Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remote unauthenticated decoding of a tiny crafted value with no interaction yields availability-only impact; PR:N and C:N/I:N since only DoS occurs, AC:L as the payload is trivial to craft.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4DescriptionCVE.org
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the univ.Real type converted its mantissa, base, and exponent value to a Python float using exact big-integer exponentiation. A BER, CER, or DER encoded REAL value only a few bytes long can carry a very large exponent, causing float conversion through prettyPrint(), str(), comparison, arithmetic, int(), or an explicit float() call to consume excessive CPU and memory and hang applications that decode untrusted ASN.1 data and then print, log, or compare decoded objects. This issue is fixed in version 0.6.4.
Articles & Coverage 1
AnalysisAI
Uncontrolled resource consumption in the pyasn1 Python ASN.1 library (versions prior to 0.6.4) lets remote attackers hang applications that decode untrusted BER/CER/DER data. A REAL value only a few bytes long can encode an enormous exponent; when the decoded univ.Real object is later printed, logged, compared, or converted via prettyPrint(), str(), int(), or float(), pyasn1 performs exact big-integer exponentiation that consumes excessive CPU and memory. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The target application must decode attacker-supplied BER/CER/DER data with pyasn1 (<0.6.4) AND subsequently trigger float conversion of a decoded univ.Real - via prettyPrint(), str()/repr(), logging, comparison, arithmetic, int(), or an explicit float() call. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (7.5, High) is internally consistent with the description: an unauthenticated remote attacker with no user interaction can trigger availability loss only (C:N/I:N), which matches a pure DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker sends a service that decodes untrusted ASN.1 (for example an LDAP, PKI/certificate, or SNMP endpoint) a tiny crafted BER/CER/DER REAL value carrying a huge exponent. When the application logs, prints, or compares the decoded object, pyasn1 attempts exact big-integer exponentiation, pinning CPU and exhausting memory until the worker hangs or the process is killed. … |
| Remediation | Vendor-released patch: pyasn1 0.6.4 - upgrade to 0.6.4 or later (e.g. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems and applications using pyasn1 versions prior to 0.6.4 by scanning requirements.txt, setup.py, and pip freeze output across your infrastructure. …
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Same weakness CWE-400 – Uncontrolled Resource Consumption
View allSame technique Denial Of Service
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External POC / Exploit Code
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