CVE-2026-39457

CVE-2026-39457 is a high-severity vulnerability in Freebsd with a CVSS 3.x base score of 7.8. 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-121.

Key facts

Description

When exchanging data over a socket, libnv uses select(2) to wait for data to arrive. However, it does not verify whether the provided socket descriptor fits in select(2)'s file descriptor set size limit of FD_SETSIZE (1024). An attacker who is able to force a libnv application to allocate large file descriptors, e.g., by opening many descriptors and executing a program which is not careful to close them upon startup, can trigger stack corruption. If the target application is setuid-root, then this could be used to elevate local privileges.

Frequently asked questions

What is CVE-2026-39457?
When exchanging data over a socket, libnv uses select(2) to wait for data to arrive. However, it does not verify whether the provided socket descriptor fits in select(2)'s file descriptor set size limit of FD_SETSIZE (1024). An attacker who is able to force a libnv application to allocate large file descriptors, e.g., by opening many descriptors and executing a program which is not careful to close them upon startup, can trigger stack corruption. If the target application is setuid-root, then this could be used to elevate local privileges.
How severe is CVE-2026-39457?
CVE-2026-39457 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-39457 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39457?
CVE-2026-39457 primarily affects Freebsd. In total, 37 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-39457?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-39457 have an EU (EUVD) identifier?
Yes. CVE-2026-39457 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26356.
When was CVE-2026-39457 published?
CVE-2026-39457 was published on 2026-04-30 and last updated on 2026-06-17.

References

Affected products (37)

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