CVE-2026-91157: Information Disclosure (CVSS 7.5)

Description

Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, sites with secure uploads enabled did not reconcile existing upload security metadata when a previously public category became read-restricted or when category permissions changed during a bulk import. Media and attachments uploaded while the category was public retained a public accessibility flag and remained reachable by anonymous users through their short upload URLs, including uploads associated with deleted topics. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0048

Probability of exploitation

0.40%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-200 CWE-200

CWE-863 Incorrect Authorization

References

Other References

https://github.com/discourse/discourse/commit/16017732981fdb3ee65d7b3c69c573610bf02aab https://github.com/discourse/discourse/commit/83f5f9f1df7ddc79ec0950e1b2038ba659635708 https://github.com/discourse/discourse/commit/98f1c021d0e956cded5239a5d8a6afe2b9e1b7e7 https://github.com/discourse/discourse/commit/b2fb98394b2636b29e850f06b0029f8ca8b48458 https://github.com/discourse/discourse/security/advisories/GHSA-298h-xgw6-4pv3

Frequently Asked Questions

What is CVE-2026-91157? +

Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, sites with secure uploads enabled did not reconcile existing upload security metadata when a previously public category became read-restricted or when category permissions changed during a bulk import. Media and attachments uploaded while the category was public retained a public accessibility flag and remained reachable by anonymous users through their short upload URLs, including uploads associated with deleted topics. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-91157? +

CVE-2026-91157 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0048, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-91157? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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