CVE-2026-59885
Description
A flaw was found in pyasn1, a Python library for Abstract Syntax Notation One (ASN.1). The BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. A remote attacker could exploit this by providing a specially crafted payload containing an OID with many arcs, leading to excessive CPU consumption and a denial of service (DoS) in applications that decode untrusted ASN.1 data. The corresponding encoders also exhibit this quadratic behavior when re-encoding attacker-supplied values.
Statement
A flaw was found in pyasn1. The BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. A small crafted payload containing an OID with many arcs consumes excessive CPU per decode() call, allowing denial of service in applications that decode untrusted ASN.1 data (certificates, LDAP, SNMP, Kerberos). The corresponding encoders exhibit the same behavior when re-encoding attacker-supplied values. The arc-size limit introduced for CVE-2026-23490 does not mitigate this issue. This issue is fixed in pyasn1 version 0.6.4.
Mitigation
Update to pyasn1 version 0.6.4 or later when available for your product stream. The impact is limited to availability (denial of service) — an attacker cannot access or modify data. Applications that do not process untrusted ASN.1 input are at reduced risk.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other); Reduce Performance
This issue can make the product perform more slowly. If an attacker can influence the number of iterations in the loop, then this performance problem might allow a denial of service by consuming more platform resources than intended.
Frequently Asked Questions
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