CVE-2026-41059 [High] | Authentication Bypass in Oauth2 Proxy

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 have a configuration-dependent authentication bypass. Deployments are affected when all of the following are true: Use of `skip_auth_routes` or the legacy `skip_auth_regex`; use of patterns that can be widened by attacker-controlled suffixes, such as `^/foo/.*/bar$` causing potential exposure of `/foo/secret`; and protected upstream applications that interpret `#` as a fragment delimiter or otherwise route the request to the protected base path. In deployments that rely on these settings, an unauthenticated attacker can send a crafted request containing a number sign in the path, including the browser-safe encoded form `%23`, so that OAuth2 Proxy matches a public allowlist rule while the backend serves a protected resource. Deployments that do not use these skip-auth options, or that only allow exact public paths with tightly scoped method and path rules, are not affected. A fix has been implemented in version 7.15.2 to normalize request paths more conservatively before skip-auth matching so fragment content does not influence allowlist decisions. Users who cannot upgrade immediately can reduce exposure by tightening or removing `skip_auth_routes` and `skip_auth_regex` rules, especially patterns that use broad wildcards across path segments. Recommended mitigations include replacing broad rules with exact, anchored public paths and explicit HTTP methods; rejecting requests whose path contains `%23` or `#` at the ingress, load balancer, or WAF level; and/or avoiding placing sensitive application paths behind broad `skip_auth_routes` rules.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-23	0.16%	0.31%	+0.15%
2	2026-04-27	0.13%	0.16%	+0.03%
3	2026-04-22	—	0.13%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-23

0.16%

0.31%

+0.15%

2026-04-27

0.13%

0.16%

+0.03%

2026-04-22

—

0.13%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.2	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	3.9	4.2	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.2

3.1

HIGH

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

3.9

4.2

[email protected]

Affected software / configurations for CVE-2026-41059

Vendor	Product	Version	Raw CPE
oauth2_proxy_project	oauth2_proxy	>= 7.5.0, < 7.15.2	cpe:2.3:a:oauth2_proxy_project:oauth2_proxy::::::::

References for CVE-2026-41059

URL	Tags
https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-pxq7-h93f-9jrg	Vendor Advisory

URL

CVE-2026-41059 | OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex

Exploit prediction scoring system (EPSS) score for CVE-2026-41059

Common vulnerability scoring system (CVSS) metrics for CVE-2026-41059

Weakness enumeration for CVE-2026-41059

GitHub Security Advisory for CVE-2026-41059

Affected software / configurations for CVE-2026-41059

References for CVE-2026-41059