VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-44681: Mcpm · Authlib OIDC Implicit/Hybrid Authorization Vulnerable to Open Redirect

Affects mcpmSource GCVE Database

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Not known to be exploited · CVSS 6.1 Medium : upgrade to 2.14.0_4 when convenient.

Data as of 30 Oct 2026, 07:00 UTC

CVSS 3.1 base score

6.1Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.14.0_4

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
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: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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 13 Aug 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 mcpm to 2.14.0_4.

Affected software

Product	Affected	Fixed in
Homebrewmcpm`pkg:brew/mcpm`Other threats	Affected >=2.1.0 <2.14.0_4	Fixed in 2.14.0_4

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

AI-suggested

A fix is available in Authlib version 2.14.0_4. Users should upgrade to this version or later to remediate the vulnerability. The patch ensures that redirect_uri is validated before any error response that issues a redirect. No additional mitigation actions are required once the update is applied.

Description

CVE-2026-44681 is an open redirect vulnerability in Authlib's OpenIDImplicitGrant and OpenIDHybridGrant authorization endpoints. An attacker can cause the authorization server to issue an HTTP 302 redirect to an arbitrary URL by submitting an authorization request that omits the required 'openid' scope. This occurs because the scope validation error redirects to an unvalidated redirect_uri supplied by the attacker. The flaw affects Authlib versions from 2.1.0 up to but not including 2.14.0_4 and is fixed in version 2.14.0_4. The vulnerability enables phishing attacks leveraging the trusted authorization server domain but does not leak tokens or codes directly.

Impact

The vulnerability allows attackers to perform open redirect attacks from a trusted authorization server domain, potentially facilitating phishing and credential harvesting by redirecting victims to malicious sites while displaying the legitimate OIDC provider's domain in the browser. This can also bypass domain-allow-list controls that trust the authorization server's domain. Although no tokens or authorization codes are leaked, the flaw violates OAuth 2.0 security best practices and can contribute to account takeover chains when combined with other issues. The severity is medium due to the phishing leverage without direct token compromise.

Summary

The vulnerability arises in Authlib's OpenIDImplicitGrant and OpenIDHybridGrant classes where the presence of the 'openid' scope is checked before validating the redirect_uri. If the 'openid' scope is missing, an InvalidScopeError is raised that includes the raw, attacker-controlled redirect_uri without validation. The OAuth2Error handler then issues an HTTP 302 redirect to this unvalidated URI, enabling an open redirect. This allows unauthenticated attackers to craft authorization requests that cause the authorization server to redirect victims to attacker-chosen URLs. The issue is a variant of a previously fixed open redirect problem but was missed in the implicit and hybrid grant flows. No user authentication or valid client_id is required to exploit this. The impact is phishing leverage due to trusted domain redirection, violating OAuth 2.0 security best practices. The vulnerability affects Authlib versions >=2.1.0 and <2.14.0_4 and is fixed in 2.14.0_4.

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Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 07:00 UTC

Technical details

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