EUVD-2026-43956Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Untrusted ASN.1 is decoded without auth or interaction (AV:N/AC:L/PR:N/UI:N); impact is CPU exhaustion or an unhandled crash with no data exposure, so A:H and C:N/I:N.
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 BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.
Articles & Coverage 1
AnalysisAI
Denial of service in the pyasn1 Python ASN.1 library (versions prior to 0.6.4) allows a remote attacker to exhaust CPU and crash applications by supplying crafted BER, CER, or DER encoded data. The shared BER decoder parses long-form tags without bounding the tag ID size, so a malicious tag forces construction of an arbitrarily large integer whose processing scales quadratically, and on Python 3.11+ triggers unhandled ValueError exceptions in integer-to-string error formatting. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires only that the target application feed attacker-controlled data to pyasn1's BER, CER, or DER decoder - no authentication, user interaction, or special configuration is needed (AV:N/AC:L/PR:N/UI:N), so any endpoint that decodes untrusted ASN.1 against a pre-0.6.4 pyasn1 is exposed. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, base 7.5) reflects a remotely triggerable, unauthenticated, low-complexity availability-only impact with no confidentiality or integrity effect - consistent with the description of a pure DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker submits a crafted certificate, SNMP packet, LDAP message, or token whose ASN.1 encoding contains a long-form tag with an excessive number of continuation octets to a network service that decodes it with pyasn1. On Python 3.11+ the decoder raises an unhandled ValueError while formatting the enormous tag ID, crashing the request or worker; on older interpreters the quadratic big-integer processing pins CPU. … |
| Remediation | Vendor-released patch: upgrade pyasn1 to version 0.6.4 or later, which introduces a MAX_TAG_OCTETS = 20 limit (rejecting tag IDs beyond ~140 bits with a PyAsn1Error) and a hexadecimal-fallback in tag string formatting to avoid the Python 3.11+ integer-to-string ValueError; see the fix commit https://github.com/pyasn1/pyasn1/commit/628e36ecbb5277a3f01572ce418ef54271b165a5 and advisory https://github.com/pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4j. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems and applications using pyasn1 library versions prior to 0.6.4 using automated dependency scanning and asset inventory tools. …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
Wazuh SIEM platform versions 4.4.0 through 4.9.0 contain an unsafe deserialization vulnerability in the DistributedAPI t
BentoML version 1.4.2 and earlier contains an unauthenticated remote code execution vulnerability through insecure deser
pgAdmin 4 contains critical remote code execution vulnerabilities in the Query Tool download and Cloud Deployment endpoi
The renderLocalView function in render/views.py in graphite-web in Graphite 0.9.5 through 0.9.10 uses the pickle Python
BentoML is a Python library for building online serving systems optimized for AI apps and model inference. Rated critica
OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h does not properly restrict processing of ChangeCiph
pyLoad download manager version prior to 0.5.0b3.dev77 exposes the Flask SECRET_KEY through an unauthenticated endpoint.
In Mercurial before 4.1.3, "hg serve --stdio" allows remote authenticated users to launch the Python debugger, and conse
Unauthenticated remote code execution in Marimo ≤0.20.4 allows attackers to execute arbitrary system commands via the `/
pyLoad is the free and open-source Download Manager written in pure Python. Rated medium severity (CVSS 5.3), this vulne
Langflow (a visual LLM pipeline builder) contains a critical unauthenticated code execution vulnerability (CVE-2026-3301
Cross-user flow execution in Langflow (< 1.9.1) lets any authenticated API-key holder run another user's flow by passing
Same weakness CWE-400 – Uncontrolled Resource Consumption
View allSame technique Denial Of Service
View allShare
External POC / Exploit Code
Leaving vuln.today