Out-of-bounds Read in Struktur Libheif
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.004 (30.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 30.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- Struktur Libheif
- Strukturag Libheif — versions < 1.22.0
Weakness classification (CWE)
References
- github.com/strukturag/libheif/security/advisories/GHSA-7f2h-cmpf-v9ww (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-32738?
- CVE-2026-32738 is a medium-severity vulnerability in Struktur Libheif, classified under Out-of-bounds Read. CVSS score: 6.5/10. Published 2026-05-19.
- How severe is CVE-2026-32738?
- Medium severity. CVSS v3 base score is 6.5 out of 10.