CVE-2026-4878: vLLM — MEDIUM

A flaw was found in libcap. A local unprivileged user can exploit a Time-of-check-to-time-of-use (TOCTOU) race condition in the `cap_set_file()` function. This allows an attacker with write access to a parent directory to redirect file capability updates to an attacker-controlled file. By doing so,...

Full CISO analysis pending enrichment.

What systems are affected?

Package	Ecosystem	Vulnerable Range	Patched
vLLM	pip	—	No patch
83.4K 130 dependents Pushed 6d ago 31% patched ~35d to patch Full package profile →
vLLM	pip	—	No patch
83.4K 130 dependents Pushed 6d ago 31% patched ~35d to patch Full package profile →
vLLM	pip	—	No patch
83.4K 130 dependents Pushed 6d ago 31% patched ~35d to patch Full package profile →
compat-libcap1	—	—	No patch
costmanagement/costmanagement-metrics-rhel9-operator	—	—	No patch
discovery/discovery-server-rhel9	—	—	No patch
discovery/discovery-ui-rhel9	—	—	No patch
insights-proxy/insights-proxy-container-rhel9	—	—	No patch
libcap	—	—	No patch
libcap-main	—	—	No patch
rhaiis/model-opt-cuda-rhel9	—	—	No patch
rhcos	—	—	No patch
rhosdt/opentelemetry-collector-rhel9	—	—	No patch
rhosdt/opentelemetry-rhel9-operator	—	—	No patch
rhosdt/opentelemetry-target-allocator-rhel9	—	—	No patch
rhui5/cds-rhel9	—	—	No patch
rhui5/haproxy-rhel9	—	—	No patch
rhui5/installer-rhel9	—	—	No patch
rhui5/rhua-rhel9	—	—	No patch

How severe is it?

CVSS 3.1

6.7 / 10

EPSS

N/A

Exploitation Status

No known exploitation

Sophistication

N/A

What is the attack surface?

AV Local

AC High

PR Low

UI Required

S Unchanged

C High

I High

A High

What should I do?

No patch available

Monitor for updates. Consider compensating controls or temporary mitigations.

Which compliance frameworks are affected?

Compliance analysis pending. Sign in for full compliance mapping when available.

Frequently Asked Questions

What is CVE-2026-4878?

A flaw was found in libcap. A local unprivileged user can exploit a Time-of-check-to-time-of-use (TOCTOU) race condition in the `cap_set_file()` function. This allows an attacker with write access to a parent directory to redirect file capability updates to an attacker-controlled file. By doing so, capabilities can be injected into or stripped from unintended executables, leading to privilege escalation.

Is CVE-2026-4878 actively exploited?

No confirmed active exploitation of CVE-2026-4878 has been reported, but organizations should still patch proactively.

How to fix CVE-2026-4878?

No patch is currently available. Monitor vendor advisories for updates.

What is the CVSS score for CVE-2026-4878?

CVE-2026-4878 has a CVSS v3.1 base score of 6.7 (MEDIUM).

What are the technical details?

Original Advisory

A flaw was found in libcap. A local unprivileged user can exploit a Time-of-check-to-time-of-use (TOCTOU) race condition in the `cap_set_file()` function. This allows an attacker with write access to a parent directory to redirect file capability updates to an attacker-controlled file. By doing so, capabilities can be injected into or stripped from unintended executables, leading to privilege escalation.

Weaknesses (CWE)

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

CWE-367 — Time-of-check Time-of-use (TOCTOU) Race Condition: The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

[Implementation] The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
[Implementation] When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.

Source: MITRE CWE corpus.