CVE-2026-31423: net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()
Vulnerability summary
CVE-2026-31423 is a medium (CVSS 5.5) Divide By Zero vulnerability in linux. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 1.8% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 31 · Related 29Timeline
- 13-04-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_hfsc: fix divide-by-zero in rtsc_min() m2sm() converts a u32 slope to a u64 scaled value. For large inputs (e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores the difference of two such u64 values in a u32 variable `dsm` and uses it as a divisor. When the difference is exactly 2^32 the truncation yields zero, causing a divide-by-zero oops in the concave-curve intersection path: Oops: divide error: 0000 RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601) Call Trace: init_ed (net/sched/sch_hfsc.c:629) hfsc_enqueue (net/sched/sch_hfsc.c:1569) [...] Widen `dsm` to u64 and replace do_div() with div64_u64() so the full difference is preserved.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.12%
Chance of exploitation in the next 30 days
Percentile
2%
Versus all other CVEs
30-day change
Decrease -0.05 pp
From 0.17% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu157 products
- linuxAll versions (No fix recorded) | < 5.15.0-186.196 | < 6.8.0-136.136
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1112.119 | < 6.8.0-1061.64
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ad8e8fec40290a8c8cf145c0deaadf76f80c5163 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 25b6821884713a31e2b49fb67b0ebd765b33e0a9 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < c56f78614e7781aaceca9bd3cb2128bf7d45c3bd | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < b9e6431cbea8bb1fae8069ed099b4ee100499835 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 17c1b9807b8a67d676b6dcf749ee932ebaa7f568 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 4576100b8cd03118267513cafacde164b498b322 | 2.6.12
- linux_kernel≥ 2.6.12.1, < 5.10.253 | ≥ 5.11, < 5.15.203 | ≥ 5.16, < 6.1.168 | ≥ 6.2, < 6.6.134 | ≥ 6.7, < 6.12.81 | ≥ 6.13, < 6.18.22 | ≥ 6.19, < 6.19.12 | 2.6.12 | 2.6.12:rc2 | 2.6.12:rc3 | 2.6.12:rc4 | 2.6.12:rc5 | 7.0:rc1 | 7.0:rc2 | 7.0:rc3 | 7.0:rc4 | 7.0:rc5 | 7.0:rc6
Debian1 product
- linux< 6.1.170-1 | < 6.12.85-1 | < 6.19.12-1
3 vendors · 160 products
