CVE-2026-75509
MEDIUMDescription
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 1% of all known CVEs.
References
Related Vulnerabilities
Other CWE-290 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-4358 | Critical | 9.8 | 97% | KEV | - |
| CVE-2022-24112 | Critical | 9.8 | 96% | KEV | Fix |
| CVE-2022-23131 | Critical | 9.1 | 96% | KEV | - |
| CVE-2021-29441 | High | 8.6 | 88% | - | Fix |
| CVE-2019-1234 | High | 7.5 | 74% | - | - |
| CVE-2021-31195 | Medium | 6.5 | 74% | - | Fix |
Common questions
How do I fix CVE-2026-75509?
Upgrade joserfc on debian unstable to 1.7.3-1 or later.
Is CVE-2026-75509 being actively exploited?
Not that we know of. CVE-2026-75509 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.09% is the estimated probability that it will be exploited in the next 30 days. That is higher than 1% of all scored CVEs.
How severe is CVE-2026-75509?
CVE-2026-75509 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-75509 affect?
Published advisories record a fix for joserfc (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.