CVE-2026-84383: Memory Corruption (CVSS 9.8)

Description

libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can make HeifPixelImage::transfer_channel_from_image_as() append duplicate Alpha planes with different bit depths to m_storage. HeifPixelImage::scale_nearest_neighbor() in libheif/image/pixelimage.cc allocates the destination Alpha plane using the first plane's 8-bit depth, then iterates a later 10-bit or 12-bit Alpha component and writes uint16_t samples into the same 8-bit allocation. The output geometry controls the overflow extent and the encoded sample values control the data written, allowing a remote file processed by heif_decode_image() to cause a heap out-of-bounds write. This issue is fixed in version 1.23.2.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0061

Probability of exploitation

0.48%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

References

Other References

https://github.com/strukturag/libheif/commit/f4fb8bde4704ebb46e46ff9fb94407c9774153b2 https://github.com/strukturag/libheif/releases/tag/v1.23.2 https://github.com/strukturag/libheif/security/advisories/GHSA-g89c-p67h-r497 https://github.com/strukturag/libheif/security/advisories/GHSA-g89c-p67h-r497

Frequently Asked Questions

What is CVE-2026-84383? +

libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can make HeifPixelImage::transfer_channel_from_image_as() append duplicate Alpha planes with different bit depths to m_storage. HeifPixelImage::scale_nearest_neighbor() in libheif/image/pixelimage.cc allocates the destination Alpha plane using the first plane's 8-bit depth, then iterates a later 10-bit or 12-bit Alpha component and writes uint16_t samples into the same 8-bit allocation. The output geometry controls the overflow extent and the encoded sample values control the data written, allowing a remote file processed by heif_decode_image() to cause a heap out-of-bounds write. This issue is fixed in version 1.23.2. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-84383? +

CVE-2026-84383 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0061, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-84383? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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