CVE-2026-118669VulnerabilityPublished 31 Oct 2026

parsedmarc · OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client

Affects parsedmarcSource GCVE Database

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Authoritative record:CVE-2026-118669· High 8.4

Not known to be exploited · CVSS 8.4 High : upgrade to 11.0.3_1 soon.

Data as of 31 Oct 2026, 16:05 UTC

CVSS 4.0 base score

8.4High

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 4.0	8.4

Patch: Available – fixed in 11.0.3_1

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: High
Vulnerable system availability: None
Subsequent system confidentiality: High
Subsequent system integrity: High
Subsequent system availability: None

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: High: There is a total loss of confidentiality, resulting in all resources within the Subsequent System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 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 30 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 parsedmarc to 11.0.3_1.

Affected software

Product	Affected	Fixed in
Homebrewparsedmarc`pkg:brew/parsedmarc`Other threats	Affected >=8.11.0 <11.0.3_1	Fixed in 11.0.3_1

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AI-suggested

A fix is available in OAuthlib version 11.0.3_1. Users should upgrade to this version or later to resolve the issue. The vulnerability arises from OAuthlib's handling of client_id in token requests; upgrading ensures that the client_id used for grant and scope validation matches the authenticated client. No additional mitigation steps are required if the fix is applied.

Description

OAuthlib contains a vulnerability in its token grant handlers where an authenticated low-privilege client can supply a different client_id in the token request body, causing the authorization checks to be performed under that other client identity. This affects the client_credentials and password grant flows. The flaw arises because OAuthlib does not require the client_id in the request body to match the authenticated client's client_id before validating grant types and scopes. As a result, a lower-privilege client can obtain tokens with broader scopes or grant types assigned to a different client. A fix is available in version 11.0.3_1.

Impact

An authenticated attacker controlling a low-privilege confidential client can obtain access tokens authorized under another client's broader grant and scope policies. This can result in unauthorized issuance of tokens with elevated scopes, use of grant types reserved for higher-privilege clients, and tokens persisting under a spoofed client_id. The attack requires valid credentials for one client and is not an unauthenticated attack. The vulnerability represents a token authorization bypass that undermines client privilege separation.

Summary

OAuthlib's token grant handlers for client_credentials and password grants authenticate a client and set request.client accordingly. However, if the request body contains a client_id parameter, OAuthlib does not overwrite it with the authenticated client's client_id before calling validate_grant_type() and validate_scopes(). This allows an attacker with credentials for a low-privilege client to submit a token request with a different client_id belonging to a higher-privilege client. The application validator, which receives the attacker-supplied client_id as the first argument, may then authorize the grant and scopes under the higher-privilege client identity despite authenticating the lower-privilege client. This inconsistency leads to token authorization bypass, enabling issuance of tokens with unauthorized scopes or grant types. The vulnerability is fixed in OAuthlib version 11.0.3_1.

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Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:05 UTC

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