# CVE-2025-38312: fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod()

Status: published. Published: 2025-07-10. Updated: 2026-11-05.

In the Linux kernel, the following vulnerability has been resolved:

fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod()

In fb_find_mode_cvt(), iff mode->refresh somehow happens to be 0x80000000,
cvt.f_refresh will become 0 when multiplying it by 2 due to overflow. It's
then passed to fb_cvt_hperiod(), where it's used as a divider -- division
by 0 will result in kernel oops. Add a sanity check for cvt.f_refresh to
avoid such overflow...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 9027ce4c037b566b658b8939a76326b7125e3627 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 610f247f2772e4f92b63442125a1b7ade79898d8 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 2d63433e8eaa3c91b2948190e395bc67009db0d9 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 54947530663edcbaaee1314c01fdd8c72861b124 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < ab91647acdf43b984824776559a452212eaeb21a (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < b235393b9f43ff86a38ca2bde6372312ea215dc5 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 53784073cbad18f75583fd3da9ffdfc4d1f05405 (affected, git); ≥ 96fe6a2109db29cd15b90a093c16e6cb4b19371a; < 3f6dae09fc8c306eb70fdfef70726e1f154e173a (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.14 (affected); ≥ 0; < 2.6.14 (unaffected, semver); ≥ 5.4.295; ≤ 5.4.* (unaffected, semver); ≥ 5.10.239; ≤ 5.10.* (unaffected, semver); ≥ 5.15.186; ≤ 5.15.* (unaffected, semver); ≥ 6.1.142; ≤ 6.1.* (unaffected, semver); ≥ 6.6.94; ≤ 6.6.* (unaffected, semver); ≥ 6.12.34; ≤ 6.12.* (unaffected, semver); ≥ 6.15.3; ≤ 6.15.* (unaffected, semver); ≥ 6.16; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-05; percentile 7.96%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/9027ce4c037b566b658b8939a76326b7125e3627 (CNA: Linux)

- https://git.kernel.org/stable/c/610f247f2772e4f92b63442125a1b7ade79898d8 (CNA: Linux)

- https://git.kernel.org/stable/c/2d63433e8eaa3c91b2948190e395bc67009db0d9 (CNA: Linux)

- https://git.kernel.org/stable/c/54947530663edcbaaee1314c01fdd8c72861b124 (CNA: Linux)

- https://git.kernel.org/stable/c/ab91647acdf43b984824776559a452212eaeb21a (CNA: Linux)

- https://git.kernel.org/stable/c/b235393b9f43ff86a38ca2bde6372312ea215dc5 (CNA: Linux)

- https://git.kernel.org/stable/c/53784073cbad18f75583fd3da9ffdfc4d1f05405 (CNA: Linux)

- https://git.kernel.org/stable/c/3f6dae09fc8c306eb70fdfef70726e1f154e173a (CNA: Linux)

- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html (ADP: CVE)

- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html (ADP: CVE)

- https://cert-portal.siemens.com/productcert/html/ssa-082556.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2025-38312; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2025-38312; retrieved 2026-11-05; source updated Not reported

Revision: ec8ac5db2abeb915f1604890132b3d1e16b55b000f5cb63e1f3525c0692cf6ab

Canonical: https://y2.dev/cve/CVE-2025-38312

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