net/sched: fq: add overflow bounds to quantum and initial quantum
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: add overflow bounds to quantum and initial quantum fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 * psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill loop adds 0 to f->credit (which stays <= 0) and goto begin loops forever under the qdisc lock, creating a soft lockup. Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product cannot wrap, then cap the result at 1 << 20, matching the bound already enforced on TCA_FQ_QUANTUM in fq_change(). Conditions to recreate the bug: a device whose MTU (plus hard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.
CVE-2026-90076
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-2026-90076
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": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
"lessThan": "fd63409b669f9951f1cc6b02486a5254103800d1",
"versionType": "git"
},
{
"status": "affected",
"version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
"lessThan": "d16dac3925be95ad46e986d4b139c9898b6e227f",
"versionType": "git"
},
{
"status": "affected",
"version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
"lessThan": "f6b3e3848a5fca63438984acd6d9eceac80814c1",
"versionType": "git"
},
{
"status": "affected",
"version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
"lessThan": "e35acd56f244d94355f9ab237c2ecc8fba5e6f04",
"versionType": "git"
},
{
"status": "affected",
"version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
"lessThan": "709f34f7c28dc4dd6c40343d101850f11e172312",
"versionType": "git"
}
],
"programFiles": [
"net/sched/sch_fq.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.12",
"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_fq.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-90076
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #48593 · Revision 1
- Added to Heist Feed
- Publisher date