VulnerabilityPublished 4 Aug 2026

CVE-2026-66884: Erlang Ecosystem Foundation oidcc_plug · Cross-Site Request Forgery (CSRF)

Affects Erlang Ecosystem Foundation oidcc_plugSource CVE Database V5

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Not known to be exploited · CVSS 2.1 Low : upgrade to 0.5.0 when convenient.

Data as of 2 Nov 2026, 10:58 UTC

CVSS 4.0 base score

2.1Low

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.5.0, 97d75afc57826dca31989b47d6e2a3c136039917

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
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: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system 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 Vulnerable System.
Vulnerable system 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 to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable 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 4 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 2 Nov 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 oidcc_plug to 0.5.0; oidcc_plug to 97d75afc57826dca31989b47d6e2a3c136039917.

Affected software

Product	Affected	Fixed in
Erlang Ecosystem Foundationoidcc_plug	Affected >=0.2.0-beta.1 <0.5.0	Fixed in 0.5.0
Erlang Ecosystem Foundationoidcc_plug	Affected ≥ e577ae73b9080693442916043a22d8f05491dd93, < 97d75afc57826dca31989b47d6e2a3c136039917	Fixed in 97d75afc57826dca31989b47d6e2a3c136039917
Hexoidcc_plug`pkg:hex/oidcc_plug`Other threats	Affected >=0.2.0-beta.1 <0.5.0	Fixed in 0.5.0

CPE configurations (1)

cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*

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AI-suggested

If you cannot patch yet, applications should ensure that callback requests without a valid session or missing state parameters are rejected and that all security checks (nonce, state, PKCE, peer IP, user agent) are enforced. Avoid reusing the same callback endpoint for both sign-in and account linking flows.

Description

CVE-2026-66884 is a Cross-Site Request Forgery (CSRF) vulnerability in the Erlang Ecosystem Foundation's oidcc_plug library, specifically in the Oidcc.Plug.AuthorizationCallback module. The flaw allows an attacker to trick a victim's browser into completing an authorization flow that the victim did not initiate, potentially signing the victim into the attacker's account. This occurs because the callback endpoint processes requests without a valid session by disabling security checks, including nonce, state, PKCE, peer IP, and user agent validations. The vulnerability affects versions from 0.2.0-beta.1 before 0.5.0 of oidcc_plug.

Impact

The vulnerability allows an attacker to cause a victim's browser to complete an authorization flow the victim did not initiate, resulting in the victim being signed into the attacker's account. This can lead to unauthorized access to the victim's actions under the attacker's identity. Additionally, if the application uses the same callback for both signing in and linking provider accounts, the attacker can link their account to the victim's, potentially leading to account takeover. The CVSS 4.0 score is low (2.1), reflecting limited impact and the requirement for user interaction.

Summary

The vulnerability in oidcc_plug arises from the Oidcc.Plug.AuthorizationCallback.call/2 function, which processes callback requests lacking an Oidcc.Plug.Authorize session by substituting permissive defaults and skipping critical security checks. An attacker can obtain an authorization code for their own account and induce a victim to visit the callback endpoint with that code but without the required state parameter. Because the application does not reject such requests and disables security validations, the victim is signed into the attacker's account. This can lead to the victim's actions being performed under the attacker's identity and, in cases where the same callback is used for sign-in and account linking, may result in account takeover. Legitimate flows always include a state parameter, so the permissive fallback serves no conforming flow. The issue affects oidcc_plug versions from 0.2.0-beta.1 up to but not including 0.5.0.

CWE-352Cross-Site Request Forgery (opens in a new tab)
Compound weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #3OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.
Architecture and Design
Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330).
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.3 (opens in a new tab)
V4.2.2 (opens in a new tab)
V13.3.2 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cross-Domain Search Timing (opens in a new tab)
Cross Site Identification (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

CPE configurations (1)

Description

AI analysisMachine-generated, updated 11 Aug 2026, 18:41 UTC

WeaknessesCWE-352

Technical details

References

Community reviews

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