How severe is CVE-2026-74900?

CVE-2026-74900 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-74900 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-74900?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-74900 published?

CVE-2026-74900 was published on 2026-08-17.

CVE-2026-74900

CVE-2026-74900 is a critical-severity vulnerability with a CVSS 3.x base score of 9.8. 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-391.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.3
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-391
Published: 2026-08-17
Last modified: 2026-08-17

Description

openssl_encrypt versions before 1.4.0 contain a critical vulnerability in pqc.py where KEM decapsulation failures silently fall back to simulation mode, generating a deterministic shared secret from only 16 bytes of the private key and publicly available encapsulated key data. Attackers who obtain 16 bytes of the private key can compute the shared secret and decrypt all ciphertext, as the fallback triggers on any KEM failure without raising an error.

Frequently asked questions

What is CVE-2026-74900?: openssl_encrypt versions before 1.4.0 contain a critical vulnerability in pqc.py where KEM decapsulation failures silently fall back to simulation mode, generating a deterministic shared secret from only 16 bytes of the private key and publicly available encapsulated key data. Attackers who obtain 16 bytes of the private key can compute the shared secret and decrypt all ciphertext, as the fallback triggers on any KEM failure without raising an error.
How severe is CVE-2026-74900?: CVE-2026-74900 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-74900 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-74900?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-74900 published?: CVE-2026-74900 was published on 2026-08-17.

References

Other CWE-391 vulnerabilities

CVE-2025-71325 — Critical (CVSS 9.8): picklescan before 0.0.27 contains a parsing logic error in the _list_globals function when handling STACK_GLOBAL…
CVE-2022-22160 — Medium (CVSS 6.5): An Unchecked Error Condition vulnerability in the subscriber management daemon (smgd) of Juniper Networks Junos OS…
CVE-2020-14383 — Medium (CVSS 6.5): A flaw was found in samba's DNS server. An authenticated user could use this flaw to the RPC server to crash. This RPC…
CVE-2022-20849 — Medium (CVSS 6.1): A vulnerability in the Broadband Network Gateway PPP over Ethernet (PPPoE) feature of Cisco IOS XR Software could…

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