Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-28386 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Openssl Openssl. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 24th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-28386 is an out-of-bounds read vulnerability affecting the OpenSSL FIPS module version 3.6, specifically in applications performing AES-CFB128 encryption or decryption on x86-64 systems equipped with AVX-512 and VAES instruction set support. The issue arises when processing partial cipher blocks, where a previous operation left an incomplete block and the current input provides fewer bytes than needed to complete it, leading to an over-read of up to 15 bytes. Other architectures or systems lacking VAES support follow unaffected code paths. The vulnerability carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is classified under CWE-125 (Out-of-bounds Read).
A remote, unauthenticated attacker can exploit this flaw by supplying crafted input that positions the input buffer at a memory page boundary, with the subsequent page unmapped. This triggers the out-of-bounds read, potentially causing a crash and denial-of-service (DoS) condition for the affected application. There is no information disclosure, as the over-read bytes are not propagated to output. Exploitation requires specific conditions, including partial block processing and precise memory alignment, and CFB mode is not used in common protocols like TLS/DTLS, which favor CBC, GCM, CCM, or ChaCha20-Poly1305.
OpenSSL's security advisory (https://openssl-library.org/news/secadv/20260407.txt) details the issue and assesses it as low severity per their policy due to the narrow attack surface. Mitigation is available via a patch in commit 61f428a2fc6671ede184a19f71e6e495f0689621 (https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621), which security practitioners should apply to vulnerable OpenSSL FIPS 3.6 deployments.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19958
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.
Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.
Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.
Routine patching replaces vulnerable code containing out-of-bounds read flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.
Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.
Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.