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pyasn1 CVE-2026-59884

| EUVDEUVD-2026-43956 HIGH
Uncontrolled Resource Consumption (CWE-400)
2026-07-14 GitHub_M GHSA-m4p7-r5rc-7g4j
Python Denial Of Service Pyasn1 Red Hat Suse
7.5
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
7.5 HIGH

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.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
5.9 MEDIUM
qualitative

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

4
Patch available
Jul 14, 2026 - 23:21 EUVD
Source Code Evidence Fetched
Jul 14, 2026 - 17:32 vuln.today
Analysis Generated
Jul 14, 2026 - 17:32 vuln.today
CVE Published
Jul 14, 2026 - 16:41 cve.org
HIGH 7.5

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 21,501 pypi packages depend on pyasn1 (481 direct, 21,133 indirect)

Ecosystem-wide dependent count for version 0.6.4.

DescriptionCVE.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

News 14 New Python Vulnerabilities - 14 High Severity, 1 With POC Jul 15, 2026

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. No public exploit identified at time of analysis, though the fix commit ships proof-of-concept test cases; not listed in CISA KEV.

Technical ContextAI

pyasn1 implements ASN.1 (Abstract Syntax Notation One) encoding/decoding used pervasively in cryptography, PKI, X.509 certificate parsing, SNMP, and LDAP tooling. In BER/CER/DER encodings, tag numbers larger than 30 are represented in 'long form' as a sequence of continuation octets, each contributing 7 bits to the tag ID. The vulnerable code in pyasn1/codec/ber/decoder.py accumulated these continuation octets with no upper bound, letting an attacker build a Python big-integer of essentially unbounded width. This is a classic CWE-400 (Uncontrolled Resource Consumption): the quadratic cost of arbitrary-precision integer arithmetic drives CPU exhaustion, and secondarily, Python 3.11+ enforces sys.get_int_max_str_digits() so rendering such a huge integer to a decimal string in error/repr paths raises an uncaught ValueError. The CPE cpe:2.3:a:pyasn1:pyasn1 confirms the pyasn1 package itself (not a downstream consumer) is the affected component.

RemediationAI

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. Because pyasn1 is frequently a transitive dependency, audit your dependency tree (pip show pyasn1 and lockfiles) and pin the fixed version across all consuming services. If immediate upgrade is not possible, compensating controls include validating or size-limiting untrusted ASN.1 input before it reaches the decoder (reject inputs containing implausibly long-form tags), restricting which network endpoints accept externally supplied DER/BER/CER blobs, and running decode operations under CPU-time or separate worker-process limits so a single malicious payload cannot starve the whole service - the trade-off being added latency and operational complexity, and none of these fully close the crash path the way the patch does.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Python 3 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4 SUSE Linux Enterprise Module for Public Cloud 15 SP4 SUSE Linux Enterprise Server 15 SP4 SUSE Manager Proxy 4.3 SUSE Manager Retail Branch Server 4.3 SUSE Manager Server 4.3 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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CVE-2026-59884 vulnerability details – vuln.today
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