CVE-2026-28386

Issue summary: Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support can trigger an out-of-bounds read of up to 15 bytes when processing partial cipher blocks.

Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not written to output.

The vulnerable code path is only reached when processing partial blocks (when a previous call left an incomplete block and the current call provides fewer bytes than needed to complete it). Additionally, the input buffer must be positioned at a page boundary with the following page unmapped. CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or ChaCha20-Poly1305 instead. For these reasons the issue was assessed as Low severity according to our Security Policy.

Only x86-64 systems with AVX-512 and VAES instruction support are affected. Other architectures and systems without VAES support use different code paths that are not affected.

OpenSSL FIPS module in 3.6 version is affected by this issue.

Database specific

{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/28xxx/CVE-2026-28386.json",
    "cna_assigner": "openssl",
    "cwe_ids": [
        "CWE-125"
    ]
}

References

Affected packages

Git / github.com/openssl/openssl

Affected ranges

Type

GIT

Repo

https://github.com/openssl/openssl

Events

Introduced

7b371d80d959ec9ab4139d09d78e83c090de9779

Fixed

fe686e15d84334b284f883118ed92f64b409b3aa

Fixed

61f428a2fc6671ede184a19f71e6e495f0689621

Database specific

{
    "cpe": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "3.6.0"
        },
        {
            "fixed": "3.6.2"
        }
    ],
    "source": [
        "CPE_RANGE",
        "REFERENCES"
    ]
}

Affected versions

3.*

3.6-POST-CLANG-FORMAT-WEBKIT

3.6-PRE-CLANG-FORMAT-WEBKIT

openssl-3.*

openssl-3.6.0

openssl-3.6.1

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-28386.json"