Security assessments indicate that CVE-2026-39886 presents a notable risk, potentially requiring prompt mitigation.
Status: Received on 21 Apr 2026, 02:16 UTC
Published on: 21 Apr 2026, 02:16 UTC
CVSS Release: version 3
security-advisories@github.com
Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVE-2026-39886: OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. Versions 3.4.0 through 3.4.9 have a signed integer overflow vulnerability in OpenEXR's HTJ2K (High-Throughput JPEG 2000) decompression path. The `ht_undo_impl()` function in `src/lib/OpenEXRCore/internal_ht.cpp` accumulates a bytes-per-line value (`bpl`) using a 32-bit signed integer with no overflow guard. A crafted EXR file with 16,385 FLOAT channels at the HTJ2K maximum width of 32,767 causes `bpl` to overflow `INT_MAX`, producing undefined behavior confirmed by UBSan. On an allocator-permissive host where the required ~64 GB allocation succeeds, the wrapped negative `bpl` value would subsequently be used as a per-scanline pointer advance, which would produce a heap out-of-bounds write. On a memory-constrained host, the allocation fails before `ht_undo_impl()` is entered. This is the second distinct integer overflow in `ht_undo_impl()`. CVE-2026-34545 addressed a different overflow in the same function — the `int16_t p` pixel-loop counter at line ~302 that overflows when iterating over channels whose `width` exceeds 32,767. The CVE-2026-34545 fix did not touch the `int bpl` accumulator at line 211, which is the subject of this advisory. The `bpl` accumulator was also not addressed by any of the 8 advisories in the 2026-04-05 v3.4.9 release batch. This finding is structurally identical to CVE-2026-34588 (PIZ `wcount*nx` overflow in `internal_piz.c`) and should be remediated with the same pattern. The CVE-2026-34588 fix did not touch `internal_ht.cpp`. Version 3.4.10 contains a remediation that addresses the vulnerability in `internal_ht.cpp`.
The exploitability of CVE-2026-39886 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
With low attack complexity and no required privileges, CVE-2026-39886 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-39886, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-39886, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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