Linux Kernel divide-by-zero in sch_hfsc rtsc_min()
CVE-2026-31423 Published on April 13, 2026
net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()
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.
Products Associated with CVE-2026-31423
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below ad8e8fec40290a8c8cf145c0deaadf76f80c5163 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 25b6821884713a31e2b49fb67b0ebd765b33e0a9 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below c56f78614e7781aaceca9bd3cb2128bf7d45c3bd is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below b9e6431cbea8bb1fae8069ed099b4ee100499835 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 17c1b9807b8a67d676b6dcf749ee932ebaa7f568 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 4576100b8cd03118267513cafacde164b498b322 is affected.
- Version 2.6.12 is affected.
- Before 2.6.12 is unaffected.
- Version 5.10.253, <= 5.10.* is unaffected.
- Version 5.15.203, <= 5.15.* is unaffected.
- Version 6.1.168, <= 6.1.* is unaffected.
- Version 6.6.134, <= 6.6.* is unaffected.
- Version 6.12.81, <= 6.12.* is unaffected.
- Version 6.18.22, <= 6.18.* is unaffected.
- Version 6.19.12, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.