CVE-2026-34379
From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, a misaligned memory write vulnerability exists in LossyDctDecoder_execute() in src/lib/OpenEXRCore/internal_dwa_decoder.h:749.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.28%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, a misaligned memory write vulnerability exists in LossyDctDecoder_execute() in src/lib/OpenEXRCore/internal_dwa_decoder.h:749. When decoding a DWA or DWAB-compressed EXR file containing a FLOAT-type channel, the decoder performs an in-place HALF→FLOAT conversion by casting an unaligned uint8_t * row pointer to float * and writing through it. Because the row buffer may not be 4-byte aligned, this constitutes undefined behavior under the C standard and crashes immediately on architectures that enforce alignment (ARM, RISC-V, etc.). On x86 it is silently tolerated at runtime but remains exploitable via compiler optimizations that assume aligned access. This vulnerability is fixed in 3.2.7, 3.3.9, and 3.4.9.
- CVSS 3.1
- 7.1 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
- EPSS
- 0.28% probability · 21th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-704, CWE-787, CWE-843, CWE-475
- Affected
- openexr/openexr
- Source
- security-advisories@github.com
References
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7Product, Release Notes
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.9Product, Release Notes
- https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.4.9Product, Release Notes
- https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-w88v-vqhq-5p24Exploit, Vendor Advisory
- https://access.redhat.com/security/cve/CVE-2026-34379
- https://bugzilla.redhat.com/show_bug.cgi?id=2455402
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34379.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.