CVE-2024-46828: Linux kernel · sched: sch_cake: fix bulk flow accounting logic for host fairness
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.4.0-1135.145~18.04.1 : patch Linux kernel soon.
Data as of 29 Oct 2026, 22:34 UTC
- Patch
- Available – fixed in 5.4.0-1135.145~18.04.1, 5.4.0-1140.147~18.04.1, 5.4.0-1139.148~18.04.1 +75
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Sep 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7088-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7119-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7123-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7144-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7154-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7155-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gkeoppkg:deb/ubuntu/linux-gkeop?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: sched: sch_cake: fix bulk flow accounting logic for host fairness In sch_cake, we keep track of the count of active bulk flows per host, when running in dst/src host fairness mode, which is used as the round-robin weight when iterating through flows. The count of active bulk flows is updated whenever a flow changes state. This has a peculiar interaction with the hash collision handling: when a hash collision occurs (after the set-associative hashing), the state of the hash bucket is simply updated to match the new packet that collided, and if host fairness is enabled, that also means assigning new per-host state to the flow. For this reason, the bulk flow counters of the host(s) assigned to the flow are decremented, before new state is assigned (and the counters, which may not belong to the same host anymore, are incremented again). Back when this code was introduced, the host fairness mode was always enabled, so the decrement was unconditional. When the configuration flags were introduced the *increment* was made conditional, but the *decrement* was not. Which of course can lead to a spurious decrement (and associated wrap-around to U16_MAX). AFAICT, when host fairness is disabled, the decrement and wrap-around happens as soon as a hash collision occurs (which is not that common in itself, due to the set-associative hashing). However, in most cases this is harmless, as the value is only used when host fairness mode is enabled. So in order to trigger an array overflow, sch_cake has to first be configured with host fairness disabled, and while running in this mode, a hash collision has to occur to cause the overflow. Then, the qdisc has to be reconfigured to enable host fairness, which leads to the array out-of-bounds because the wrapped-around value is retained and used as an array index. It seems that syzbot managed to trigger this, which is quite impressive in its own right. This patch fixes the issue by introducing the same conditional check on decrement as is used on increment. The original bug predates the upstreaming of cake, but the commit listed in the Fixes tag touched that code, meaning that this patch won't apply before that.
References
- ubuntu.com/security/CVE-2024-46828 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-46828 (opens in a new tab)
- git.kernel.org/linus/546ea84d07e3e324644025e2aae2d12ea4c5896e (opens in a new tab)
- git.kernel.org/stable/c/4a4eeefa514db570be025ab46d779af180e2c9bb (opens in a new tab)
- git.kernel.org/stable/c/7725152b54d295b7da5e34c2f419539b30d017bd (opens in a new tab)
- git.kernel.org/stable/c/cde71a5677971f4f1b69b25e854891dbe78066a4 (opens in a new tab)
- git.kernel.org/stable/c/549e407569e08459d16122341d332cb508024094 (opens in a new tab)
- git.kernel.org/stable/c/d4a9039a7b3d8005b90c7b1a55a306444f0e5447 (opens in a new tab)
- git.kernel.org/stable/c/d7c01c0714c04431b5e18cf17a9ea68a553d1c3c (opens in a new tab)
- git.kernel.org/stable/c/546ea84d07e3e324644025e2aae2d12ea4c5896e (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7119-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7123-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7144-1 (opens in a new tab)