CVE Intelligence
Medium Authentication

CVE-2026-114617 — Authlib: ID token can disable its own nonce validation via the nonce_supported claim

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, OpenIDMixin.parse_id_token() reads the nonce_supported decision from the untrusted ID token being validated and sets the expected nonce to null when that claim is the JSON boolean false. In implicit and hybrid relying parties, or applications that directly accept externally supplied ID tokens, an attacker with a captured validly signed token can bypass the nonce-to-session binding and replay the victim's token into an attacker-controlled session. Plain authorization code flow is not affected, and the token must still pass signature, issuer, and audience validation. OpenIDMixin.parse_id_token() trusts nonce_supported in both authlib/integrations/base_client/sync_openid.py and authlib/integrations/base_client/async_openid.py to disable the expected nonce. This issue is fixed in version 1.9.0.

Published Oct 22, 2026 · Updated Oct 23, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.2% (30-day exploitation probability)+2
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.23%
ahead of 14% of scored CVEs · Oct 26, 2026
Affects
Authlib
Authlib
CVSS base
4.2
Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Authlib Authlib).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  5. Search available logs for exploit probes matching the vulnerability class (authentication), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Authlib Authlib version < 1.9.0 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
4.2 CVSS 3.1 Medium 1.6 2.5 security-advisories@github.com via NIST National Vulnerability Database
4.2 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-294 · Authentication Bypass by Capture-replay

Other CVEs with this weakness →

EPSS over time FIRST

Oct 23, 2026 → Oct 26, 2026 · 4 reading(s) · max 0.23%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Review authentication logs: logins without MFA, anomalous sessions and recently created accounts.
web/proxy/WAF logsnetwork IDS/IPSauthentication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Received → Undergoing Analysis
    Oct 23, 2026 · NIST National Vulnerability Database
  • SSVC assessment updated
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · Published → Received
    Oct 22, 2026 · NIST National Vulnerability Database
  • Record published
    Oct 22, 2026
  • CVSS changed · 4.2
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
  • CVE published
    Oct 22, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 22, 2026 – Oct 22, 2026

References

4 on the record

Elsewhere on this site

Authlib
every CVE for this vendor
Authentication
same class
CWE-294
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-114620 Authlib: Unvalidated request_uri fetch in JWT-secured authorization request (JAR) leading to SSRF 4d
  • CVE-2026-114616 Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512) 4d
  • CVE-2026-114615 Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys 4d
  • CVE-2026-114618 Authlib: Default JWT bearer grant accepts assertions for the wrong audience 4d
  • CVE-2026-114619 Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens 4d
  • CVE-2026-114614 Authlib: is_secure_transport() loopback exemption can be bypassed with a userinfo component, allowing cleartext-HTTP URLs to non-loopback hosts 4d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-114617 is "Authlib: ID token can disable its own nonce validation via the nonce_supported claim", rated Medium. It affects Authlib (Authlib); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.2 describes technical severity. EPSS 0.23% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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