cbcvebase.
CVE-2018-6126
published 2019-01-09

CVE-2018-6126: A precision error in Skia in Google Chrome prior to 67.0.3396.62 allowed a remote attacker to perform an out of bounds memory write via a crafted HTML page.

PriorityP259high8.8CVSS 3.0
AVNACLPRNUIRSUCHIHAH
EXPLOIT
EPSS
7.67%
93.8th percentile
A precision error in Skia in Google Chrome prior to 67.0.3396.62 allowed a remote attacker to perform an out of bounds memory write via a crafted HTML page.

Affected

9 ranges
VendorProductVersion rangeFixed in
debiandebian_linux
debiandebian_linux
debianfirefox< firefox 60.0.2-1 (sid)firefox 60.0.2-1 (sid)
debianfirefox-esr< firefox 60.0.2-1 (sid)firefox 60.0.2-1 (sid)
googlechrome< 67.0.3396.6267.0.3396.62
googlechrome>= unspecified < 67.0.3396.6267.0.3396.62
redhatenterprise_linux_desktop
redhatenterprise_linux_server
redhatenterprise_linux_workstation

Detection & IOCsextracted from sources · hover to see the quote

versionGoogle Chrome < 67.0.3396.62
  • The exploit path involves SkScan::FillPath → walk_convex_edges → SkARGB32_Shader_Blitter::blitH writing out-of-bounds. Crash signatures in ASan/UBSan logs will reference SkScan_Path.cpp and SkEdge.cpp in the Skia library stack trace.
  • UBSan runtime error signature to look for in crash telemetry: 'left shift of negative value -1' originating from SkPixmap.h, indicating the out-of-bounds X coordinate (-1) reached the pixel write path.
  • ASan heap-buffer-overflow crash signature: WRITE of size 4 immediately past a 400-byte heap region, triggered from Sk4fLinearGradient.cpp shadeSpan path — useful for correlating crash dumps.
  • The vulnerability is exploitable via a crafted SVG with cubic bezier paths (cubicTo) using near-zero negative coordinates (e.g., -31/64) combined with a linear gradient shader. Detection of such SVG patterns in web content may indicate exploitation attempts.
  • ·The heap overflow only triggers when anti-aliasing is turned OFF in Skia. Deployments or configurations that force anti-aliasing on are not affected by this specific code path.
  • ·Both Chrome and Firefox are affected via their shared use of the Skia library. Firefox ESR 52 and ESR 60 are also listed as vulnerable; the fix for Firefox landed in 60.0.2.
  • ·Red Hat Enterprise Linux 8 Firefox package is listed as Not Affected; patching priority should focus on RHEL 6/7 and Fedora systems running unpatched Firefox or Chromium.

CVSS provenance

nvdv3.08.8HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
nvdv2.06.8MEDIUMAV:N/AC:M/Au:N/C:P/I:P/A:P
osv8.8HIGH
vendor_debian8.8HIGH
vendor_redhat8.8HIGH
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