EUVD-2026-43955Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remote unauthenticated attacker (AV:N/PR:N/UI:N) with a simple crafted OID (AC:L) causes CPU-exhaustion DoS; availability-only impact (A:H, C/I:N) with no scope change.
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, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs, so a small crafted payload containing an OID with many arcs consumes excessive CPU per decode() call and can deny service to applications that decode untrusted ASN.1 data. The corresponding encoders have the same quadratic behavior when an application re-encodes previously decoded attacker-supplied values. This issue is fixed in version 0.6.4.
Articles & Coverage 1
AnalysisAI
Denial of service in the pyasn1 Python ASN.1 library (all versions prior to 0.6.4) allows remote attackers to exhaust CPU by submitting a small crafted OBJECT IDENTIFIER or RELATIVE-OID whose arcs are decoded in quadratic time, so any application that calls decode() on untrusted ASN.1 data can be stalled per call; re-encoding such values triggers the same blow-up. Rated CVSS 7.5 (availability-only) with no confidentiality or integrity impact; no public exploit identified at time of analysis, though the fix commit ships a regression test that effectively demonstrates the trigger. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The only prerequisite is that the target application passes attacker-influenced data to pyasn1's BER/CER/DER decoder.decode() (or re-encodes previously decoded attacker values through the encoder) on a version earlier than 0.6.4. … 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) is internally consistent with the description: an unauthenticated remote attacker can trigger the condition with low complexity and no user interaction, but impact is confined to availability - there is no data disclosure or code execution. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker sends a small crafted DER/BER blob containing an OBJECT IDENTIFIER with thousands of arcs (for example the 4096 single-byte-arc payload used in the fix's regression test) to a network service that decodes untrusted ASN.1, such as an LDAP or SNMP endpoint or a certificate/token validator. Each decode() call spends quadratic CPU on that tiny input, and a handful of concurrent requests can saturate worker processes and deny service to legitimate users. … |
| Remediation | Vendor-released patch: upgrade pyasn1 to version 0.6.4 or later (pip install --upgrade 'pyasn1>=0.6.4'), and update any downstream packages or lockfiles that transitively pin an older pyasn1; see the advisory at https://github.com/pyasn1/pyasn1/security/advisories/GHSA-8ppf-4f7h-5ppj and release https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: identify and inventory all systems, applications, and transitive dependencies using pyasn1, prioritizing internet-facing services that handle LDAP, SNMP, X.509, or PKI protocols. …
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View allSame technique Denial Of Service
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External POC / Exploit Code
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