high 7.8

CVE-2024-26737 json

bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel

published 2024-04-03 2 y ago modified 2026-08-05 3 mo ago also EUVD-2024-23999

cvss: 7.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

The following race is possible between bpf_timer_cancel_and_free and bpf_timer_cancel. It will lead a UAF on the timer->timer.

bpf_timer_cancel(); spin_lock(); t = timer->time; spin_unlock();

bpf_timer_cancel_and_free(); spin_lock(); t = timer->timer; timer->timer = NULL; spin_unlock(); hrtimer_cancel(&t->timer); kfree(t);

/* UAF on t */ hrtimer_cancel(&t->timer);

In bpf_timer_cancel_and_free, this patch frees the timer->timer after a rcu grace period. This requires a rcu_head addition to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init, this does not need a kfree_rcu because it is still under the spin_lock and timer->timer has not been visible by others yet.

In bpf_timer_cancel, rcu_read_lock() is added because this helper can be used in a non rcu critical section context (e.g. from a sleepable bpf prog). Other timer->timer usages in helpers.c have been audited, bpf_timer_cancel() is the only place where timer->timer is used outside of the spin_lock.

Another solution considered is to mark a t->flag in bpf_timer_cancel and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free, it busy waits for the flag to be cleared before kfree(t). This patch goes with a straight forward solution and frees timer->timer after a rcu grace period.

Patch / fix

fixed in 1 distros 6 links 5

Linux Linux 5.15.150, 6.1.80, 6.6.19, 6.7.7, 6.8

debian ubuntu red hat suse almalinux rocky linux

linux Debian 12 6.1.82-1
linux Debian 14, Debian 13 6.7.7-1

debian advisories DEBIAN-CVE-2024-26737

linux Ubuntu 22.04 LTS 5.15.0-112.122
linux-aws Ubuntu 22.04 LTS 5.15.0-1063.69
linux-gcp Ubuntu 22.04 LTS 5.15.0-1062.70
linux-gke Ubuntu 22.04 LTS 5.15.0-1060.66
linux-ibm Ubuntu 22.04 LTS 5.15.0-1056.59
linux-kvm Ubuntu 22.04 LTS 5.15.0-1060.65
linux-azure Ubuntu 22.04 LTS 5.15.0-1066.75
linux-gkeop Ubuntu 22.04 LTS 5.15.0-1046.53

ubuntu advisories UBUNTU-CVE-2024-26737

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel RHEL 9 5.14.0-427.28.1.el9_4
rv RHEL 9 5.14.0-427.28.1.el9_4
perf RHEL 9 5.14.0-427.28.1.el9_4
rtla RHEL 9 5.14.0-427.28.1.el9_4
bpftool RHEL 9 7.3.0-427.28.1.el9_4
libperf RHEL 9 5.14.0-427.28.1.el9_4
kernel-rt RHEL 9 5.14.0-427.28.1.el9_4
kernel-64k RHEL 9 5.14.0-427.28.1.el9_4

red hat advisories RHSA-2024:5066 RHSA-2024:5067 RHSA-2024:4928

kernel-source Linux Micro 6.0 6.4.0-18.1
kernel-default Linux Micro 6.0 6.4.0-18.1
kernel-kvmsmall Linux Micro 6.0 6.4.0-18.1
kernel-default-base Linux Micro 6.0 6.4.0-17.1.1.51
kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.5.1
kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.5.1
kernel-rt_debug Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.5.1
kernel-source-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.5.1

suse advisories SUSE-SU-2025:20008-1 SUSE-SU-2024:2973-1 SUSE-SU-2024:2203-1 SUSE-SU-2024:2135-1 SUSE-SU-2024:1663-1 SUSE-SU-2024:1659-1

kernel AlmaLinux 9 5.14.0-427.28.1.el9_4
rv AlmaLinux 9 5.14.0-427.28.1.el9_4
perf AlmaLinux 9 5.14.0-427.28.1.el9_4
rtla AlmaLinux 9 5.14.0-427.28.1.el9_4
bpftool AlmaLinux 9 7.3.0-427.28.1.el9_4
libperf AlmaLinux 9 5.14.0-427.28.1.el9_4
kernel-rt AlmaLinux 9 5.14.0-427.28.1.el9_4
kernel-64k AlmaLinux 9 5.14.0-427.28.1.el9_4

almalinux advisories ALSA-2024:4928

kernel Rocky Linux 9 5.14.0-427.28.1.el9_4.cloud.1.0
kernel Rocky Linux 9 5.14.0-427.28.1.el9_4

rocky linux advisories RXSA-2024:4928 RLSA-2024:4928

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2024-26737 updated 2026-11-05 cvss 5.5

kernel: bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel

Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
affected: workaround, no fix planned “Out of support scope”
Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
affected: workaround, no fix available
Red Hat CodeReady Linux Builder EUS (v.9.2) kernel-debuginfo-common-s390x 5.14.0-284.77.1.el9_2, kernel-debuginfo-common-x86_64 5.14.0-284.77.1.el9_2, kernel-debuginfo-common-aarch64 5.14.0-284.77.1.el9_2, kernel-debuginfo-common-ppc64le 5.14.0-284.77.1.el9_2
fixed: vendor fix RHSA-2024:5066
Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-427.28.1.el9_4, perf 5.14.0-427.28.1.el9_4, rtla 5.14.0-427.28.1.el9_4, kernel-devel-matched 5.14.0-427.28.1.el9_4, kernel-64k-devel-matched 5.14.0-427.28.1.el9_4, kernel-debug-devel-matched 5.14.0-427.28.1.el9_4, +6 more
fixed: vendor fix RHSA-2024:4928
Red Hat Enterprise Linux AppStream EUS (v.9.2) perf 5.14.0-284.77.1.el9_2, rtla 5.14.0-284.77.1.el9_2, kernel-devel-matched 5.14.0-284.77.1.el9_2, kernel-64k-devel-matched 5.14.0-284.77.1.el9_2, kernel-debug-devel-matched 5.14.0-284.77.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.77.1.el9_2, +5 more
fixed: vendor fix RHSA-2024:5066
Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.3.0-427.28.1.el9_4, kernel 5.14.0-427.28.1.el9_4, kernel-64k 5.14.0-427.28.1.el9_4, kernel-core 5.14.0-427.28.1.el9_4, kernel-tools 5.14.0-427.28.1.el9_4, python3-perf 5.14.0-427.28.1.el9_4, +28 more
fixed: vendor fix RHSA-2024:4928
Red Hat Enterprise Linux BaseOS EUS (v.9.2) bpftool 7.0.0-284.77.1.el9_2, kernel 5.14.0-284.77.1.el9_2, kernel-64k 5.14.0-284.77.1.el9_2, kernel-core 5.14.0-284.77.1.el9_2, kernel-tools 5.14.0-284.77.1.el9_2, python3-perf 5.14.0-284.77.1.el9_2, +28 more
fixed: vendor fix RHSA-2024:5066
Red Hat Enterprise Linux CRB (v. 9) libperf 5.14.0-427.28.1.el9_4, kernel-debuginfo-common-s390x 5.14.0-427.28.1.el9_4, kernel-debuginfo-common-x86_64 5.14.0-427.28.1.el9_4, kernel-debuginfo-common-aarch64 5.14.0-427.28.1.el9_4, kernel-debuginfo-common-ppc64le 5.14.0-427.28.1.el9_4 Red Hat Enterprise Linux NFV (v. 9) kernel-rt 5.14.0-427.28.1.el9_4, kernel-rt-kvm 5.14.0-427.28.1.el9_4, kernel-rt-core 5.14.0-427.28.1.el9_4, kernel-rt-modules 5.14.0-427.28.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.28.1.el9_4, kernel-rt-debug-core 5.14.0-427.28.1.el9_4, +6 more
fixed: vendor fix RHSA-2024:4928

show 3 more

Red Hat Enterprise Linux Real Time EUS (v.9.2) kernel-rt 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-core 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-modules 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-debug-core 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-modules-core 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-debug-modules 5.14.0-284.77.1.rt14.362.el9_2, +4 more Red Hat Enterprise Linux Real Time for NFV EUS (v.9.2) kernel-rt 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-kvm 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-core 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-modules 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-debug-kvm 5.14.0-284.77.1.rt14.362.el9_2, kernel-rt-debug-core 5.14.0-284.77.1.rt14.362.el9_2, +6 more
fixed: vendor fix RHSA-2024:5067
Red Hat Enterprise Linux RT (v. 9) kernel-rt 5.14.0-427.28.1.el9_4, kernel-rt-core 5.14.0-427.28.1.el9_4, kernel-rt-modules 5.14.0-427.28.1.el9_4, kernel-rt-debug-core 5.14.0-427.28.1.el9_4, kernel-rt-modules-core 5.14.0-427.28.1.el9_4, kernel-rt-debug-modules 5.14.0-427.28.1.el9_4, +4 more
fixed: vendor fix RHSA-2024:4928
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux AppStream EUS (v.9.2) kernel-doc 5.14.0-284.77.1.el9_2
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 y ago (2024-04-03)

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.8	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Weakness

CWE-416 Use After Free

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2024-26737
NVD CVE-2024-26737

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary