CVE-2026-58098: freebsd Memory Corruption — Fix

Description

When semop(2) blocks waiting for a semaphore condition, it releases the per-set lock and sleeps. Upon waking, it checks the sequence number embedded in the semaphore set's IPC identifier to detect whether the set was removed while the caller was asleep. This sequence number is only 15 bits wide. If enough semaphore sets are created and destroyed in the same table slot while a caller is blocked, the counter wraps around, and semop(2) may falsely conclude that the original set still exists. The subsequent access to a semaphore within the set may then be out of bounds. An unprivileged local user can trigger an out-of-bounds access on kernel heap memory, potentially leading to privilege escalation.

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CVSS v3.1 Score

8.4

HIGH

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

EPSS — Exploit Prediction

0.0011

Probability of exploitation

0.01%

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-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All

References

Advisories & Patches

https://security.freebsd.org/advisories/FreeBSD-SA-26:64.sysvsem.asc

Frequently Asked Questions

What is CVE-2026-58098? +

When semop(2) blocks waiting for a semaphore condition, it releases the per-set lock and sleeps. Upon waking, it checks the sequence number embedded in the semaphore set's IPC identifier to detect whether the set was removed while the caller was asleep. This sequence number is only 15 bits wide. If enough semaphore sets are created and destroyed in the same table slot while a caller is blocked, the counter wraps around, and semop(2) may falsely conclude that the original set still exists. The subsequent access to a semaphore within the set may then be out of bounds. An unprivileged local user can trigger an out-of-bounds access on kernel heap memory, potentially leading to privilege escalation. It has a CVSS v3.1 base score of 8.4 (HIGH).

How severe is CVE-2026-58098? +

CVE-2026-58098 has a CVSS v3.1 score of 8.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0011, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-58098? +

CVE-2026-58098 affects products from freebsd, specifically: freebsd. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-58098? +

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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