CVE-2026-59885 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in pyasn1. A fix is available for pyasn1 — see the affected versions and patch details below.
pyasn1: Quadratic complexity in OBJECT IDENTIFIER and RELATIVE-OID processing allows denial of service
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59885.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-59885 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 390,807 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
pyasn1Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The BER/CER/DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. A small crafted payload (tens of kilobytes) containing an OID with many arcs consumes seconds of CPU per decode() call, allowing denial of service in any application that decodes untrusted ASN.1 data (certificates, LDAP, SNMP, Kerberos, etc.). The corresponding encoders have the same quadratic behavior, reachable when an application re-encodes previously decoded attacker-supplied values.
The arc-size limit introduced for CVE-2026-23490 bounds the byte length of an individual arc but not the number of arcs, so it does not mitigate this issue.
Affected components
ObjectIdentifierPayloadDecoder and RelativeOIDPayloadDecoder in pyasn1/codec/ber/decoder.py; ObjectIdentifierEncoder and RelativeOIDEncoder in pyasn1/codec/ber/encoder.py. The CER and DER codecs inherit these and are equally affected.
Patches
Fixed in pyasn1 0.6.4: arc accumulation in both decoders and encoders now runs in linear time.
Workarounds
Limit the size of untrusted ASN.1 input before decoding.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyasn1 | all versions | 0.6.4pip install --upgrade 'pyasn1==0.6.4' |
Affected Products
pyasn1pyasn1Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyasn1, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyasn1 to 0.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59885 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
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…
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.Source: Red Hat security advisory for CVE-2026-59885 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.5 for RHEL 8 | python3.12-pyasn1-0:0.6.4-1.el8ap | RHSA-2026:50319 |
| Red Hat Ansible Automation Platform 2.6 for RHEL 9 | python3.12-pyasn1-0:0.6.4-1.el9ap | RHSA-2026:50336 |
| Red Hat AI Inference Server 3.3 | rhaiis/model-opt-cuda-rhel9:1787601159 | RHSA-2026:59518 |
| Red Hat AI Inference Server 3.4 | rhaii/vllm-rocm-rhel9:1791856725 | RHSA-2026:83121 |
| Red Hat Enterprise Linux AI 3.3 | rhelai3/disk-image-cuda-rhel9:1788290314 | RHSA-2026:62335 |
| Red Hat Enterprise Linux AI 3.3 | rhelai3/bootc-aws-cuda-rhel9:1788273908 | RHSA-2026:62336 |
| Red Hat Hardened Images | jaeger-main-2.19.0-1.1.hum1 | RHSA-2026:40236 |
| Red Hat Migration Toolkit for Applications 8.2 | mta/mta-rhel9-operator:1786481481 | RHSA-2026:56347 |
Frequently Asked Questions
Is CVE-2026-59885 in your dependencies?
Find it across PyPI, including transitive dependencies.