net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue
In the Linux kernel, the following vulnerability has been resolved: net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a packet when the current backlog plus the packet length fits within the queue limit: sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (gred default VQ) gred_backlog+qdisc_pkt_len(skb) <= q->limit (gred configured VQ) sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (bfifo) sch->qstats.backlog + skb->len <= q->limit (plug) sch->qstats.backlog and q->backlog are u32, and qdisc_pkt_len()/skb->len are unsigned int, so all sums are computed in 32 bits and wrap at 2^32. Once the true backlog exceeds 4 GiB the wrapped sum becomes small and admission keeps succeeding, so the queue grows without bound and the kernel can be driven to OOM. Promote the sums to u64 so admission stops once the true backlog exceeds the limit. The limit is u32, so the bounded queue stays below 2^32 and the stored u32 backlog never wraps. The bug can only be reproduced as root (albeit with ridiculous setup): attach a gred (or bfifo/plug) qdisc with a limit near 4 GiB, leaving the default VQ unconfigured (for gred), and drive >4 GiB of queued traffic (e.g. via a size table / stab to inflate qdisc_pkt_len, or sustained high-rate traffic). The u32 backlog+len sum wraps at 2^32, admission keeps succeeding, and the queue grows unboundedly to OOM.
CVE-2026-90109
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-90109
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8",
"lessThan": "c5ca77024812563fe15c4f7aa906791c3683e9fd",
"versionType": "git"
},
{
"status": "affected",
"version": "a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8",
"lessThan": "3fb51b3960342bbee563543f8d33710fd0fb5a96",
"versionType": "git"
},
{
"status": "affected",
"version": "a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8",
"lessThan": "8b2d8c70b969bf84f9e248bfaf2a7135129f2eb6",
"versionType": "git"
},
{
"status": "affected",
"version": "a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8",
"lessThan": "d98b92f3d57976ae185238946ec5ea0be32195aa",
"versionType": "git"
},
{
"status": "affected",
"version": "a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8",
"lessThan": "4c660ee8c809637909f4f7eb1017f7b9401c75c4",
"versionType": "git"
}
],
"programFiles": [
"net/sched/sch_fifo.c",
"net/sched/sch_gred.c",
"net/sched/sch_plug.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.2"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.2",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.52",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/sched/sch_fifo.c",
"net/sched/sch_gred.c",
"net/sched/sch_plug.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-90109
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #48605 · Revision 1
- Added to Heist Feed
- Publisher date