Critical Security Flaw in curl Package: Authentication Bypass and Information Disclosure
Summary
ALSA-2026:55439: Important: curl security update. Affects curl versions < 7.76.1-40.el9_8.5. Fixed in 7.76.1-40.el9_8.5. How to fix ↓
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Background
The curl package is an essential tool that provides the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP. It is widely used in various applications and systems for its versatility and reliability in handling data transfers. However, recent vulnerabilities have been identified that could compromise the security of applications relying on this package, making it crucial for users to stay informed and updated.
Vulnerability Detail
The identified vulnerabilities in the curl package include an authentication bypass due to incorrect connection reuse with Negotiate authentication (CVE-2026-1965), information disclosure via OAuth2 bearer token leakage during HTTP(S) redirect (CVE-2026-3783), a man-in-the-middle attack via SSH host key bypass (CVE-2026-9547), and insecure connection establishment due to TLS configuration mismatch (CVE-2026-8286). These vulnerabilities can lead to unauthorized access, data leakage, and potential exploitation by malicious actors.
How To Fix
Minimum fixed version
7.76.1-40.el9_8.5
This is the first release that contains the fix.
sudo dnf update curlTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can disable the affected authentication methods or avoid using OAuth2 bearer tokens in redirects until the package is updated. However, this is not a long-term solution and updating the package is strongly recommended.
Conclusion
The vulnerabilities identified in the curl package pose significant security risks, including authentication bypass and information disclosure. Users are strongly encouraged to update to the latest patched version to mitigate these risks. Utilizing tools like Vulert can help in monitoring and managing open-source vulnerabilities effectively.
See every vulnerability recorded for curl →
FAQ
The vulnerabilities can lead to unauthorized access, data leakage, and potential exploitation by attackers, compromising the security of applications using curl.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without needing to sign up.
If immediate updates are not possible, consider implementing temporary workarounds such as disabling affected authentication methods or avoiding OAuth2 bearer tokens in redirects.
While specific exploits may not be publicly available, the nature of the vulnerabilities suggests that they could be exploited by attackers to gain unauthorized access or leak sensitive information.
It is advisable to regularly check for vulnerabilities, ideally on a weekly basis, and to stay updated with security patches for all critical packages.
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