CVE-2026-106110: ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer
ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ImageSharpto a version that resolves this vulnerability.Fixed in 4.1.2
Event History
Frequently Asked Questions
Which applications are exposed to this issue?
Applications using SixLabors ImageSharp versions from 2.0.0 through 4.1.1 are affected when they encode narrow 1-bit TIFF images with CCITT Group 3 Fax compression. The vulnerable compression can be selected directly or inherited from metadata when decoding and re-encoding TIFF files.
What does an attacker need to exploit the flaw?
An attacker needs influence over an image encoding workflow, such as supplying a TIFF that the application decodes and re-encodes, or controlling input that is encoded as a narrow 1-bit TIFF using CCITT Group 3 Fax compression. No authentication or user interaction is indicated by the supplied severity vector.
What is the likely impact?
The encoder can write beyond its logical compressed-output span, corrupting process memory and terminating the process. The supplied vector rates the impact as availability-only, with no confidentiality or integrity impact indicated.
What should be done if upgrading is not immediately possible?
Avoid using CCITT Group 3 Fax compression for narrow 1-bit TIFF output, including workflows that preserve or inherit compression settings from decoded TIFF metadata. Restrict or disable processing of attacker-controlled TIFF files in decode-and-re-encode pipelines where possible.
How can teams determine whether they are affected?
Review ImageSharp dependencies for versions 2.0.0 through 4.1.1 and identify TIFF encoding paths. Pay particular attention to code that explicitly selects TiffCompression.CcittGroup3Fax or re-encodes TIFF files while retaining decoded metadata; version 4.1.2 contains the fix.