CVE-2026-33525

CVE-2026-33525 is a medium-severity vulnerability in Authelia with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Description

Authelia is an open-source authentication and authorization server providing two-factor authentication and single sign-on (SSO) for applications via a web portal. In version 4.39.15, an attacker may potentially be able to inject javascript into the Authelia login page if several conditions are met simultaneously. Unless both the `script-src` and `connect-src` directives have been modified it's almost impossible for this to have a meaningful impact. However if both of these are and they are done so without consideration to their potential impact; there is a are situations where this vulnerability could be exploited. This is caused to the lack of neutralization of the `langauge` cookie value when rendering the HTML template. This vulnerability is likely difficult to discover though fingerprinting due to the way Authelia is designed but it should not be considered impossible. The additional requirement to identify the secondary application is however likely to be significantly harder to identify along side this, but also likely easier to fingerprint. Users should upgrade to 4.39.16 or downgrade to 4.39.14 to mitigate the issue. The overwhelming majority of installations will not be affected and no workarounds are necessary. The default value for the Content Security Policy makes exploiting this weakness completely impossible. It's only possible via the deliberate removal of the Content Security Policy or deliberate inclusion of clearly noted unsafe policies.

Frequently asked questions

What is CVE-2026-33525?
Authelia is an open-source authentication and authorization server providing two-factor authentication and single sign-on (SSO) for applications via a web portal. In version 4.39.15, an attacker may potentially be able to inject javascript into the Authelia login page if several conditions are met simultaneously. Unless both the `script-src` and `connect-src` directives have been modified it's almost impossible for this to have a meaningful impact. However if both of these are and they are done so without consideration to their potential impact; there is a are situations where this vulnerability could be exploited. This is caused to the lack of neutralization of the `langauge` cookie value when rendering the HTML template. This vulnerability is likely difficult to discover though fingerprinting due to the way Authelia is designed but it should not be considered impossible. The additional requirement to identify the secondary application is however likely to be significantly harder to identify along side this, but also likely easier to fingerprint. Users should upgrade to 4.39.16 or downgrade to 4.39.14 to mitigate the issue. The overwhelming majority of installations will not be affected and no workarounds are necessary. The default value for the Content Security Policy makes exploiting this weakness completely impossible. It's only possible via the deliberate removal of the Content Security Policy or deliberate inclusion of clearly noted unsafe policies.
How severe is CVE-2026-33525?
CVE-2026-33525 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-33525 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (13th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33525?
CVE-2026-33525 affects Authelia. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33525?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-33525 have an EU (EUVD) identifier?
Yes. CVE-2026-33525 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16353.
When was CVE-2026-33525 published?
CVE-2026-33525 was published on 2026-03-26 and last updated on 2026-06-17.

References

Affected products (1)

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