CVE-2026-32738

Description

libheif is a HEIF and AVIF file format decoder and encoder. In versions 1.21.2 and below, a crafted 792-byte HEIF sequence file with samples_per_chunk=0 in the stsc box causes an unsigned integer underflow in the Chunk constructor (m_last_sample = 0 + 0 - 1 = UINT32_MAX), mapping all samples to an empty chunk and resulting in a denial of service. When any sample is accessed, the library reads from index 0 of an empty std::vector, causing a guaranteed SEGV (null-page read). The file parses successfully without producing an error; the crash occurs on the first frame access. This issue has been fixed in version 1.22.0.

CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0006

Probability of exploitation

0.18%

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-125 Out-of-bounds Read

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
struktur	libheif	< 1.22.0

References

Advisories & Patches

https://github.com/strukturag/libheif/security/advisories/GHSA-7f2h-cmpf-v9ww https://github.com/strukturag/libheif/security/advisories/GHSA-7f2h-cmpf-v9ww

Exploits

https://github.com/strukturag/libheif/security/advisories/GHSA-7f2h-cmpf-v9ww https://github.com/strukturag/libheif/security/advisories/GHSA-7f2h-cmpf-v9ww

Frequently Asked Questions

What is CVE-2026-32738? +

libheif is a HEIF and AVIF file format decoder and encoder. In versions 1.21.2 and below, a crafted 792-byte HEIF sequence file with samples_per_chunk=0 in the stsc box causes an unsigned integer underflow in the Chunk constructor (m_last_sample = 0 + 0 - 1 = UINT32_MAX), mapping all samples to an empty chunk and resulting in a denial of service. When any sample is accessed, the library reads from index 0 of an empty std::vector, causing a guaranteed SEGV (null-page read). The file parses successfully without producing an error; the crash occurs on the first frame access. This issue has been fixed in version 1.22.0. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-32738? +

CVE-2026-32738 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0006, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-32738? +

CVE-2026-32738 affects products from struktur, specifically: libheif. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-32738? +

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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