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Fencer Vulns
medium 6.8

CVE-2026-49265 json

OAuthLib: Timing Attack Vulnerability in PKCE code_verifier Comparison

published 2026-09-29 40 d ago modified 2026-10-16 23 d ago also GHSA-xpv3-w29h-x7cv , PYSEC-2026-4114 , EUVD-2026-98833

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

Summary

OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. From 3.0.0 until 4.0.0, OAuthLib's PKCE checks in oauthlib/oauth2/rfc6749/grant_types/authorization_code.py compare attacker-supplied code_verifier values with stored challenges using ordinary string equality in code_challenge_method_plain and code_challenge_method_s256. Because the comparison can return after a length difference or the first mismatching character, repeated token endpoint measurements can reveal common-prefix timing information that could potentially allow recovery of the code_verifier, unauthorized access-token acquisition, and account takeover. Practical exploitation requires an intercepted, single-use authorization code and enough measurements to overcome real-world network noise; the local timing benchmark does not establish practical remote account takeover, so the weakness remains a defense-in-depth concern. This issue is fixed in version 4.0.0.

Patch / fix

  • pypi oauthlib 4.0.0
  • python-oauthlib SLE Module for Python 3 15 SP7, SLE Module for Public Cloud 15 SP4 3.2.2-150400.12.10.1
  • python-oauthlib SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.2.2-160000.3.1
  • python-oauthlib Linux Micro 6.0 3.2.2-159998.1.1

suse advisories SUSE-SU-2026:4810-1SUSE-SU-2026:24189-1SUSE-SU-2026:24246-1SUSE-SU-2026:24139-1

  • python-oauthlib openSUSE Leap 16.0 3.2.2-160000.3.1

opensuse advisories openSUSE-SU-2026:22103-1

  • python-oauthlib Azure Linux 3.0 3.2.2-4

azure linux advisories AZL-108045

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-49265 updated cvss 6.8

oauthlib: oauthlib: Timing attack vulnerability in PKCE code_verifier/code_challenge comparison allows authorization code recovery

  • Red Hat Confidential Compute Attestation openshift-sandboxed-containers/osc-podvm-builder-rhel9 Red Hat Fence Agents Remediation Operator workload-availability/fence-agents-remediation-rhel9-operator Red Hat Lightspeed Core lightspeed-core/lightspeed-stack-rhel9 Red Hat Lightspeed Services for Advanced Cluster Management lightspeed-services-acm/ocp-rules-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-rhel9-operator Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-rhel8-operator
    +24 more products
    Red Hat Migration Toolkit for Virtualization migration-toolkit-virtualization/mtv-rhel9-operator Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-service-api-rhel9, openshift-lightspeed/lightspeed-agentic-sandbox-rhel9, openshift-lightspeed/lightspeed-to-dataverse-exporter-rhel9 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9-operator Red Hat Pen Drive Powered by Red Hat Lightspeed pen-drive/pen-drive-scanner-rhel9 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/volsync-rhel9, rhacm2/volsync-operator-bundle Red Hat AI Inference Server rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaiis/vllm-cuda-rhel9 Red Hat Ansible Automation Platform 2 python-oauthlib 3.1.1-2.el8pc, python3.11-oauthlib 3.2.2-1.el9ap, python3.12-oauthlib 3.2.2-2.el9ap, automation-controller 4.7.17-1.el9ap, ansible-automation-platform-24/hub-rhel8, ansible-automation-platform-25/hub-rhel8, +47 more Red Hat Ceph Storage 7 rhceph/rhceph-7-rhel9 Red Hat Ceph Storage 8 rhceph/rhceph-8-rhel9 Red Hat Ceph Storage 9 rhceph/rhceph-9-rhel9 Red Hat Discovery 2 discovery/discovery-server-rhel9 Red Hat Enterprise Linux 8 fence-agents, fence-agents-all, fence-agents-apc, fence-agents-aws, fence-agents-eps, fence-agents-gce, +43 more Red Hat Enterprise Linux 9 fence-virt, fence-virtd, fence-agents, fence-virtd-cpg, fence-virtd-tcp, fence-agents-all, +52 more Red Hat Enterprise Linux 10 python-oauthlib 3.1.1-2.el8pc Red Hat OpenShift AI (RHOAI) rhoai/rhai-cli-rhel9, rhoai/odh-automl-rhel9, rhoai/odh-mlflow-rhel9, rhoai/odh-autorag-rhel9, rhoai/odh-kserve-agent-rhel9, rhoai/odh-kserve-router-rhel9, +31 more Red Hat OpenShift Container Platform 4 python-oauthlib 3.1.1-2.el8pc, openshift4/ose-ansible-rhel9-operator Red Hat OpenShift Container Platform 5 openshift5/ose-ansible-rhel9-operator Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9 Red Hat OpenStack Platform 17.1 rhosp-rhel9/openstack-keystone, rhosp-rhel9/openstack-cinder-api Red Hat OpenStack Platform 18.0 rhoso/openstack-keystone-rhel9, rhoso/openstack-cinder-api-rhel9 Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 satellite/iop-advisor-backend-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/bootc-automation-portal-rhel9 Red Hat Service Telemetry Framework 1.5 stf/smart-gateway-rhel9-operator, stf/service-telemetry-rhel9-operator
    affected: workaround, no fix available “Fix deferred”
  • Red Hat AI Inference Server 3.5 rhaii/vllm-cpu-rhel9 1791473614, rhaii/vllm-cuda-rhel9 1791473631
    fixed: vendor fix RHSA-2026:82415
  • Red Hat Enterprise Linux AI 3.5 rhelai3/bootc-cuda-rhel9 1793135861, rhelai3/bootc-aws-cuda-rhel9 1793194817, rhelai3/bootc-gcp-cuda-rhel9 1793194815, rhelai3/disk-image-cuda-rhel9 1793206758, rhelai3/bootc-azure-cuda-rhel9 1793194815
    fixed: vendor fix RHSA-2026:92452
  • Red Hat Ceph Storage 4 rhceph/rhceph-4-rhel8 Red Hat Enterprise Linux 8 python3-oauthlib Red Hat Enterprise Linux AI 3.5 rhelai3/bootc-rocm-rhel9 1793135863, rhelai3/bootc-azure-rocm-rhel9 1793194834 Red Hat Lightspeed Services for OCP lightspeed-services-ocp/ocp-rules-rhel9 Red Hat OpenShift Container Platform 4 openshift4/ose-ansible-operator Red Hat OpenStack Platform 16.2 rhosp-rhel8/openstack-tempest, rhosp-rhel8/openstack-keystone, rhosp-rhel8/openstack-cinder-api, rhosp-rhel8/openstack-mistral-api, rhosp-rhel8/openstack-mistral-base, rhosp-rhel8/openstack-mistral-engine, +2 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
26 d ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
OSV 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
GitHub 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi oauthlib
>=3.0.0, <4.0.0
4.0.0

Affected products

  • oauthlib oauthlib

Classification

Weakness
  • CWE-208 Observable Timing Discrepancy

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.