CVE-2026-40575: OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-40575 is a critical-severity flaw (CVSS 9.1) affecting oauth2 proxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-auth-route` is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can r

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 59%)
CISA exploited list	No
Weakness	CWE-290
Published	2026-04-22
Last modified	2026-07-15

Publisher (CNA): GitHub, Inc. · Vendor: oauth2 proxy project

Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-22 00:16 UTCPublished CVE record published
2026-07-15 02:21 UTCUpdated Record last modified

oauth2 proxy project oauth2 proxy UPGRADE

Affected: >= 7.5.0 and < 7.15.2

Fixed in: 7.15.2

Safe to downgrade to: a release before 7.5.0

1. Check installed version

apt-cache policy oauth2-proxy || rpm -q oauth2-proxy || oauth2-proxy --version

2. UPGRADE to 7.15.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade oauth2-proxy

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade oauth2-proxy

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 7.5.0 (Debian / Ubuntu)

apt-cache madison oauth2-proxy sudo apt install oauth2-proxy=<VERSION_BEFORE_7.5.0> sudo apt-mark hold oauth2-proxy

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list oauth2-proxy sudo dnf downgrade oauth2-proxy-<VERSION_BEFORE_7.5.0> sudo dnf versionlock add oauth2-proxy

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40575?

oauth2 proxy: upgrade to 7.15.2. Exact commands for each OS are on this page.

Is CVE-2026-40575 being exploited?

CVE-2026-40575 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40575 affect?

CVE-2026-40575 affects oauth2 proxy. Severity is critical (CVSS 9.1). OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-aut

How urgent is CVE-2026-40575?

Priority 47/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-34457 CRITICAL 9.1 UPGRADE OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers
CVE-2026-34454 LOW 3.5 UPGRADE OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers
CVE-2026-41059 HIGH 8.2 UPGRADE OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers
CVE-2026-40574 MEDIUM 6.8 UPGRADE OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers

References

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