libheif CVE-2026-41069

Exploitation requires that the target application process a specially crafted HEIF file containing a sequence track where stco.entry_count 0, saio.entry_count 0, and saiz.sample_count > 0 - this specific combination of box values is the necessary trigger. User interaction is required per CVSS UI:R: a user or automated job must open or ingest the malicious file. No authentication is required (CVSS PR:N), and no non-default configuration is needed beyond the application simply using libheif for HEIF/AVIF decoding. Exploitation is limited to denial of service (application crash); confidentiality and integrity are not impacted per the CVSS vector. Deployments that process only AVIF still-image files without sequence tracks are not exposed to this specific code path. Applications that validate or strip sequence-type boxes before passing data to libheif would also not be affected.

CVSS 3.1 scores this 6.5 (Medium). The vector AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H shows broad network reachability with no authentication or privilege requirement, but user interaction is mandatory - exploitation cannot proceed without a user or automated pipeline actively opening the malicious file. Real-world risk is therefore contingent on how libheif is deployed: embedded in a browser or OS image subsystem, the UI:R bar is trivially met by browsing to or downloading a crafted image; invoked as a backend server-side transcoder with untrusted input, the UI:R criterion may effectively be absent in practice because the 'user' is an automated job. No EPSS data was provided in the supplied intelligence. KEV status is not listed, meaning CISA has not confirmed active exploitation. No public proof-of-concept has been identified at time of analysis. Impact is purely availability (application crash / DoS); confidentiality and integrity are unaffected per CVSS. The advisory tags list 'Information Disclosure', which conflicts with CVSS C:N - this inconsistency should be verified with the vendor, as some out-of-bounds read primitives can leak memory contents before crashing. Overall, this is a genuine medium-priority issue for any deployment that processes untrusted HEIF files, but without active exploitation evidence it does not warrant emergency-level response.

An attacker crafts a malformed HEIF sequence file with stco.entry_count set to zero and saiz.sample_count set to a non-zero value, then distributes it via email attachment, web download, or a malicious image-sharing link. When a user opens the file in any application embedding libheif 1.21.2 or earlier - such as an image viewer, browser, or media importer - the SampleAuxInfoReader constructor dereferences the empty chunks vector, triggering an out-of-bounds read that crashes the hosting process. No public exploit code has been identified at time of analysis, but the parsing path is straightforward to reach and the triggering conditions are precisely described in the advisory, lowering the bar for independent exploit development.