Description
libschrift through 0.10.2 contains a divide by zero vulnerability that allows attackers to crash applications by supplying a font with unitsPerEm of 0 in the head table. Attackers can provide a crafted TrueType font whose NaN glyph coordinates bypass clip_points(), causing an out-of-bounds raster read in draw_line() during sft_render() and crashing the process.
References7
- github.com/tomolt/libschrift/blob/v0.10.2/schrift.c#L1422-L1503
- github.com/tomolt/libschrift/blob/v0.10.2/schrift.c#L542
- github.com/tomolt/libschrift/issues/46
- hackmd.io/@haind-pwn/libschrift-unitsperem-zero-oob
- www.vulncheck.com/advisories/libschrift-through-0.10.2-divide-b…
- github.com/tomolt/libschrift/issues/46
- hackmd.io/@haind-pwn/libschrift-unitsperem-zero-oob
Metrics
- CVSS 3.1
-
5.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - CVSS 4.0
-
6.8
MEDIUM
Score source: CNA
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 20 · as of 11 November 2026
- CWE
- CWE-369
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.