CVE-2026-75870
CRITICALDescription
Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret. The session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key. An attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 40% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1394 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-48956 | Critical | 9.8 | 0.9% | - | - |
| CVE-2025-44954 | Critical | 9.0 | 0.7% | - | Fix |
| CVE-2024-11619 | Medium | 5.0 | 0.7% | - | - |
| CVE-2024-29037 | Critical | 9.1 | 0.6% | - | Fix |
| CVE-2023-6451 | High | 8.6 | 0.5% | - | Fix |
| CVE-2025-41742 | Critical | 9.8 | 0.5% | - | - |
Common questions
How do I fix CVE-2026-75870?
No published fix for CVE-2026-75870 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-75870 being actively exploited?
Not that we know of. CVE-2026-75870 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.49% is the estimated probability that it will be exploited in the next 30 days. That is higher than 40% of all scored CVEs.
How severe is CVE-2026-75870?
CVE-2026-75870 has a CVSS v3 base score of 9.1, rated critical. 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.
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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 2026-08-26.