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Mallory
HighPublic exploit

Memory corruption in libjxl decoder grayscale color transformation with LCMS2

IdentifiersCVE-2026-1837CWE-787

CVE-2026-1837 is a memory-corruption vulnerability in libjxl's decoder triggered by a specially crafted image file. The flaw occurs when the decoder performs color transformation of grayscale images to another grayscale color space while using LCMS2 as the color management system (CMS) engine. In this code path, buffers allocated for 1 float per pixel are incorrectly treated as though they were allocated for 3 floats per pixel, causing pixel data to be written into uninitialized and unallocated memory. Shortly afterward, data from another uninitialized and unallocated region is copied into pixel data buffers. The issue affects software that embeds or links against vulnerable libjxl code, including Apple software via AppleJPEG as noted in Apple advisories.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation by processing a maliciously crafted image can cause denial of service via process crash or abnormal termination. Because the flaw involves invalid memory writes and subsequent copying from invalid memory regions, it also creates process-memory corruption conditions that may have broader exploitability depending on allocator behavior, platform hardening, and surrounding application context. Apple advisories specifically describe the practical impact as denial-of-service when processing a maliciously crafted image.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, avoid using LCMS2 as the CMS engine for libjxl where feasible and select the alternative CMS engine via build flags. Restrict or disable grayscale color-space transformations for untrusted JXL inputs if operationally possible. Isolate image decoding in a sandboxed, low-privilege process and treat all externally supplied image files as untrusted. Additional input filtering and decoder isolation can reduce exposure until patched builds are deployed.

Remediation

Patch, then assume compromise.

Update libjxl to a vendor-fixed release addressing CVE-2026-1837 / GHSA-76gx-97cq-65f5 once available from the upstream or downstream vendor. Rebuild and redeploy all affected applications and libraries that statically or dynamically link vulnerable libjxl code. Where applicable, verify whether the build uses LCMS2 as the CMS engine and ensure patched builds are propagated through dependent image-processing components such as AppleJPEG or other image pipelines.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Cms LittleLcms2application
Libxl ProjectLibjxlapplication
LittlecmsLcms2application

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

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Social activity3

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