CVE-2026-28386
Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support
Description
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.
INFO
Published Date :
April 7, 2026, 10:16 p.m.
Last Modified :
April 24, 2026, 6:28 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update OpenSSL FIPS module to the latest version.
- Apply relevant security patches for the module.
- Verify system has AVX-512 and VAES support.
- Test for DoS after applying updates.
Public PoC/Exploit Available at Github
CVE-2026-28386 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-28386.
| URL | Resource |
|---|---|
| https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621 | Patch |
| https://openssl-library.org/news/secadv/20260407.txt | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-28386 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-28386
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Tracking Vulnerabilities That Appear to be Credited to the Anthropic Research Team
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-28386 vulnerability anywhere in the article.
-
TheCyberThrone
OpenSSL 3.6.2: The Moderate Severity Wave
OpenSSL 3.6.2 landed this week carrying eight CVE fixes, with the project rating the most severe issue as Moderate. On the surface, that sounds reassuring—no critical exploits, no ransomware-grade zer ... Read more
-
CybersecurityNews
Multiple OpenSSL Vulnerabilities Exposes Sensitive Data in RSA KEM Handling
OpenSSL has released a broad April 2026 security update that fixes seven vulnerabilities across supported branches, led by CVE-2026-31790, a moderate-severity flaw in RSA KEM RSASVE encapsulation that ... Read more
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Help Net Security
OpenSSL 3.6.2 lands with eight CVE fixes
OpenSSL 3.6.2 patches eight CVEs across a range of components. The project rates the most severe issue in the release as Moderate. What got fixed The release fixes incorrect failure handling in RSA KE ... Read more
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Daily CyberSecurity
OpenSSL Issues Major Security Advisory: RSA and Memory Vulnerabilities Fixed
OpenSSL has released a comprehensive security advisory detailing seven vulnerabilities ranging from Moderate to Low severity. The report, dated April 7, 2026, highlights critical fixes for modern vers ... Read more
The following table lists the changes that have been made to the
CVE-2026-28386 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Reanalysis by [email protected]
Apr. 24, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Removed CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H -
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.2 Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621 Types: Patch Added Reference Type OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260407.txt Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 10, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H -
New CVE Received by [email protected]
Apr. 07, 2026
Action Type Old Value New Value Added Description 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. Added CWE CWE-125 Added Reference https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621 Added Reference https://openssl-library.org/news/secadv/20260407.txt