CVE Catalog

CVE-2025-37890

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.17%

7th percentile - higher than 7% of all known CVEs

Summary

In the Linux kernel, the HFSC network scheduler has a use-after-free vulnerability when an HFSC class has a netem child qdisc. The check cl->qdisc->q.qlen == 0 does not guarantee the class hasn't been inserted into vttree/eltree, leading to double insertion and UAF.

Risk Assessment

An attacker can exploit this to gain unauthorized access to kernel memory, potentially leading to privilege escalation or system crash.

Recommendation

Apply the Linux kernel patch that adds a check of the n_active variable to prevent double insertion into vttree/eltree.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

Vulnerability data from NVD (NIST) · CISA KEV · EPSS