VulnerabilityPublished 29 Oct 2026

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

Affects mcp-atlassianSource GCVE Database

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Authoritative record:CVE-2026-114617· Medium 4.2

Not known to be exploited · CVSS 4.2 Medium : upgrade to 0.23.1_2 when convenient.

Data as of 30 Oct 2026, 08:32 UTC

CVSS 3.1 base score

4.2Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	4.2

Patch: Available – fixed in 0.23.1_2

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade mcp-atlassian to 0.23.1_2.

Affected software

Product	Affected	Fixed in
Homebrewmcp-atlassian`pkg:brew/mcp-atlassian`Other threats	Affected >=0.11.11 <0.23.1_2	Fixed in 0.23.1_2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Authlib to version 0.23.1_2 or later, where the nonce_supported claim is read from server metadata or client configuration rather than from the token payload, preventing tokens from disabling nonce validation. Until upgraded, do not rely on tokens to indicate nonce support. No other mitigations are documented.

Description

Authlib versions prior to 0.23.1_2 contain a vulnerability in the OpenID ID token parsing logic where the nonce validation can be bypassed if the ID token includes a nonce_supported claim set to boolean false. This causes the nonce check to be skipped, allowing replay of a valid signed ID token into an attacker-controlled session, authenticating the attacker as the victim. The issue affects implicit and hybrid flows and direct calls to parse_id_token(), but not the authorization code flow. A fix is available in version 0.23.1_2.

Impact

An attacker who can supply a validly signed ID token containing nonce_supported set to false can bypass nonce validation, enabling replay attacks that authenticate the attacker as the victim at the relying party. This compromises session integrity in implicit and hybrid OpenID Connect flows or any application calling parse_id_token() directly. The authorization code flow is not affected. The impact is limited to authentication bypass via nonce validation bypass.

Summary

The vulnerability exists in Authlib's OpenIDMixin.parse_id_token() method, which reads the nonce_supported claim from the ID token payload. If this claim is boolean false, the expected nonce is set to None, causing the nonce validation to be skipped. This allows an attacker to replay a captured, validly signed ID token with a mismatched nonce, authenticating as the victim. The flaw affects all framework integrations using the vulnerable code. The nonce_supported claim is read from the token itself, which is attacker-controllable, rather than from server metadata or client configuration. The issue was introduced to accommodate a provider emitting this claim but inadvertently allows tokens to disable nonce validation. The vulnerability is fixed in Authlib version 0.23.1_2 by moving the nonce_supported flag check to server metadata rather than the token payload.

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Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 08:32 UTC

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