ΠΠΏΠΈΡΠ°Π½ΠΈΠ΅
In the Linux kernel, the following vulnerability has been resolved:
net_sched: ets: Fix double list add in class with netem as child qdisc
As described in Gerrard's report [1], there are use cases where a netem
child qdisc will make the parent qdisc's enqueue callback reentrant.
In the case of ets, there won't be a UAF, but the code will add the same
classifier to the list twice, which will cause memory corruption.
In addition to checking for qlen being zero, this patch checks whether
the class was already added to the active_list (cl_is_active) before
doing the addition to cater for the reentrant case.
[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
A use-after-free vulnerability was found in the Linux kernelβs netem qdisc. This issue occurs when it incorrectly manages duplicated packets in classful parent qdiscs. This leads to a corrupted internal state and eventual dereferencing of freed memory, resulting in unpredictable behavior, system instability, or a crash.
ΠΡΡΠ΅Ρ
A logic flaw in the ETS (Enhanced Transmission Selection) scheduler in the Linux kernelβs net/sched subsystem allows the same class to be added twice to the active list if the enqueue callback is reentered, for example due to a netem child. Although no UAF occurs, this leads to list corruption, which may result in kernel memory corruption, undefined behavior, or system crashes. Triggering this bug requires a crafted qdisc hierarchy and interaction between ETS and netem. An attacker could create memory corruption via list pointers, but turning this into privilege escalation would require further primitives or info leaks. Likely exploitable for denial-of-service (DoS) in most practical scenarios.
ΠΠ΅ΡΡ ΠΏΠΎ ΡΠΌΡΠ³ΡΠ΅Π½ΠΈΡ ΠΏΠΎΡΠ»Π΅Π΄ΡΡΠ²ΠΈΠΉ
If ETS (Enhanced Transmission Selection) scheduler not being used, then the mitigation would be to disabled related Kernel module. To mitigate this issue, prevent module sch_ets from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically. sch_ets
ΠΠ°ΡΡΠΎΠ½ΡΡΡΠ΅ ΠΏΠ°ΠΊΠ΅ΡΡ
| ΠΠ»Π°ΡΡΠΎΡΠΌΠ° | ΠΠ°ΠΊΠ΅Ρ | Π‘ΠΎΡΡΠΎΡΠ½ΠΈΠ΅ | Π Π΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΡ | Π Π΅Π»ΠΈΠ· |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 10 | kernel | Fixed | RHSA-2025:14510 | 25.08.2025 |
| Red Hat Enterprise Linux 8 | kernel-rt | Fixed | RHSA-2025:13961 | 18.08.2025 |
| Red Hat Enterprise Linux 8 | kernel | Fixed | RHSA-2025:13960 | 18.08.2025 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2025:14420 | 25.08.2025 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2025:14420 | 25.08.2025 |
| Red Hat Enterprise Linux 9.4 Extended Update Support | kernel | Fixed | RHSA-2025:15668 | 11.09.2025 |
ΠΠΎΠΊΠ°Π·ΡΠ²Π°ΡΡ ΠΏΠΎ
ΠΠΎΠΏΠΎΠ»Π½ΠΈΡΠ΅Π»ΡΠ½Π°Ρ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΡ
Π‘ΡΠ°ΡΡΡ:
EPSS
7 High
CVSS3
Π‘Π²ΡΠ·Π°Π½Π½ΡΠ΅ ΡΡΠ·Π²ΠΈΠΌΠΎΡΡΠΈ
In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of ets, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of ets, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
net_sched: ets: Fix double list add in class with netem as child qdisc
In the Linux kernel, the following vulnerability has been resolved: n ...
In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of ets, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
EPSS
7 High
CVSS3