CVE-2024-6839: corydolphin/flask-cors version 4.0.1 contains an improper regex path matching vulnerability

This week

MEDIUM 5.3REMOTEDOWNGRADE

CVE-2024-6839 is a medium-severity flaw (CVSS 5.3) 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 4.0.1 contains an improper regex path matching vulnerability. The plugin prioritizes longer regex patterns over more specific ones when matching paths, which can lead to less restrictive CORS policies being applied to sensitive endpoints. This mismatch in regex pattern priority allows unauthorized cross-origin access to sensitive data or functionality, potentially exposing confidential information and increasing the

Why this priority

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	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 45%)
CISA exploited list	No
Weakness	CWE-41
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-2024-6839?

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

Is CVE-2024-6839 being exploited?

CVE-2024-6839 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-2024-6839 affect?

CVE-2024-6839 affects flask-cors. Severity is medium (CVSS 5.3). corydolphin/flask-cors version 4.0.1 contains an improper regex path matching vulnerability. The plugin prioritizes longer regex patterns over more specific ones when matching paths, which can lead to less restrictive CORS policies being ap

How urgent is CVE-2024-6839?

Priority 42/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Flask vulnerabilities

Related CVEs

CVE-2024-6866 HIGH 7.5 DOWNGRADE corydolphin/flask-cors version 4.01 contains a vulnerability where the request path matching is case-insensiti
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-2024-6221 HIGH 7.5 DOWNGRADE A vulnerability in corydolphin/flask-cors version 4.0.1 allows the `Access-Control-Allow-Private-Network` CORS
CVE-2024-1681 MEDIUM 5.3 DOWNGRADE corydolphin/flask-cors is vulnerable to log injection when the log level is set to debug

References

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