CVE-2024-6866: corydolphin/flask-cors version 4.01 contains a vulnerability where the request path matching is case-insensiti

This week

HIGH 7.5REMOTEDOWNGRADE

CVE-2024-6866 is a high-severity flaw (CVSS 7.5) affecting flask-cors. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

corydolphin/flask-cors version 4.01 contains a vulnerability where the request path matching is case-insensitive due to the use of the `try_match` function, which is originally intended for matching hosts. This results in a mismatch because paths in URLs are case-sensitive, but the regex matching treats them as case-insensitive. This misconfiguration can lead to significant security vulnerabilities, allowing unauthorized origins to access paths m

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Weakness	CWE-178
Published	2025-03-20
Last modified	2026-06-17

Publisher (CNA): huntr.dev · Vendor: flask-cors project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-03-20 10:15 UTCPublished CVE record published
2026-06-17 08:18 UTCUpdated Record last modified

flask-cors project flask-cors DOWNGRADE

Affected: 4.0.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0.1

1. Check installed version

apt-cache policy flask-cors || rpm -q flask-cors || flask-cors --version

2. No fixed release: DOWNGRADE to a release before 4.0.1 (Debian / Ubuntu)

apt-cache madison flask-cors sudo apt install flask-cors=<VERSION_BEFORE_4.0.1> sudo apt-mark hold flask-cors

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list flask-cors sudo dnf downgrade flask-cors-<VERSION_BEFORE_4.0.1> sudo dnf versionlock add flask-cors

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-2024-6866?

flask-cors: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2024-6866 being exploited?

CVE-2024-6866 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-2024-6866 affect?

CVE-2024-6866 affects flask-cors. Severity is high (CVSS 7.5). corydolphin/flask-cors version 4.01 contains a vulnerability where the request path matching is case-insensitive due to the use of the `try_match` function, which is originally intended for matching hosts. This results in a mismatch because

How urgent is CVE-2024-6866?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Flask vulnerabilities

Related CVEs

CVE-2024-6844 MEDIUM 5.3 DOWNGRADE A vulnerability in corydolphin/flask-cors version 4.0.1 allows for inconsistent CORS matching due to the handl
CVE-2024-6839 MEDIUM 5.3 DOWNGRADE corydolphin/flask-cors version 4.0.1 contains an improper regex path matching vulnerability
CVE-2024-6221 HIGH 7.5 DOWNGRADE A vulnerability in corydolphin/flask-cors version 4.0.1 allows the `Access-Control-Allow-Private-Network` CORS

References

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