VulnerabilityPublished 21 Apr 2026Updated 15 Jul 2026

CVE-2026-40575: oauth2-proxy · Authentication Bypass by Spoofing

Affects oauth2-proxySource GCVE Database

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Not known to be exploited · CVSS 9.1 Critical : upgrade to 7.15.2 as a priority.

Data as of 12 Nov 2026, 01:33 UTC

CVSS 3.1 base score

9.1Critical

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

Sources agree

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	9.1
ADP (redhat-SADP)	CVSS 3.1	8.7

Patch: Available – fixed in 7.15.2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: None: The vulnerable system can be exploited without any interaction from any user.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
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 impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 21 Apr 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 11 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 oauth2-proxy to 7.15.2.

Affected software

Product	Affected	Fixed in
oauth2-proxy oauth2-proxy	Affected >=7.5.0 <7.15.2	Fixed in 7.15.2

AI-suggested

A fix is available in oauth2-proxy version 7.15.2. Users should upgrade to this version to remediate the vulnerability. For those unable to upgrade immediately, mitigations include: (1) stripping any client-provided X-Forwarded-Uri header before it reaches oauth2-proxy; (2) overwriting the X-Forwarded-Uri header with the actual request URI at the reverse proxy or load balancer (e.g., using nginx proxy_set_header directive); (3) restricting direct client access to oauth2-proxy so it is only accessible through a trusted reverse proxy; and (4) removing or narrowing --skip-auth-regex or --skip-auth-route rules where possible. These mitigations reduce the risk of header spoofing and unauthorized access.

Description

OAuth2 Proxy versions 7.5.0 through 7.15.1 contain an authentication bypass vulnerability when configured with --reverse-proxy and either --skip-auth-regex or --skip-auth-route. An attacker can spoof the X-Forwarded-Uri header, causing OAuth2 Proxy to evaluate authentication rules against a manipulated path, allowing unauthorized access to protected routes without a valid session. The issue is fixed in version 7.15.2. Mitigations include stripping or overwriting the X-Forwarded-Uri header before it reaches OAuth2 Proxy, restricting direct client access, and narrowing skip-auth rules.

Impact

An unauthenticated remote attacker can bypass authentication and access protected routes without a valid session if oauth2-proxy is configured with --reverse-proxy and skip-auth rules. This results in a high impact on data confidentiality and integrity for services behind the proxy. The attacker must be able to spoof the X-Forwarded-Uri header and have knowledge of the skip-auth routes or regex patterns. There is no impact on availability.

CWE-290Authentication Bypass by Spoofing (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
OWASP Cheat Sheets
REST Security (opens in a new tab)
JSON Web Token for Java (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V3.5.1 (opens in a new tab)
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
Attack patterns
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Web Services API Signature Forgery Leveraging Hash Function Extension Weakness (opens in a new tab)
Signature Spoof (opens in a new tab)
Signature Spoofing by Misrepresentation (opens in a new tab)
Session Credential Falsification through Prediction (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

Description

AI analysisMachine-generated, updated 12 Nov 2026, 01:33 UTC

WeaknessesCWE-290

Technical details

References

Community reviews

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