# CVE-2026-45445 — OpenSSL

> As of 2026-06-10, CVE-2026-45445 is a HIGH-severity vulnerability in OpenSSL, CVSS v3.1 7.5, EPSS 0.7% (51.9th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-45445, most recently “HollowByte: OpenSSL Pre-Authentication TLS DoS Flaw Bloats Server Memory With 11-Byte Payload”.

**Last updated:** 2026-06-10

## What is CVE-2026-45445?

Issue summary: When an application drives an AES-OCB context through the public EVP_Cipher() one-shot interface, the application-supplied initialisation vector (IV) is silently discarded. Impact summary: Every message encrypted under the same key uses the same effective nonce regardless of the IV supplied by the caller, resulting in (key, nonce) reuse and loss of confidentiality. If the same code path is used to compute the authentication tag, the tag depends only on the (key, IV) pair and not on the plaintext or ciphertext, allowing universal forgery of arbitrary ciphertext from a single captured message. OpenSSL provides two ways to drive a cipher: the documented streaming interface (EVP_CipherUpdate / EVP_CipherFinal_ex) and a lower-level one-shot, EVP_Cipher(), whose documentation explicitly recommends against use by applications in favour of EVP_CipherUpdate() and EVP_CipherFinal_ex(). The OCB provider's streaming handler flushes the application-supplied IV into the OCB context before processing data; the one-shot handler did not. Every call to EVP_Cipher() on an AES-OCB context therefore ran with the all-zero key-derived offset state left by cipher initialisation, regardless of the caller's IV. If EVP_EncryptFinal_ex() is subsequently used to obtain the authentication tag, the deferred IV setup runs at that point and clears the running checksum that should have been accumulated over the plaintext. The resulting tag is a function of (key, IV) only and verifies against any ciphertext produced under the same (key, IV) pair. The OpenSSL SSL/TLS implementation is not affected: AES-OCB is not a TLS cipher suite, and libssl does not call EVP_Cipher() in any case. Applications that drive AES-OCB through the documented streaming AEAD API (EVP_CipherUpdate / EVP_CipherFinal_ex) are not affected. Only applications that combine the AES-OCB cipher with the EVP_Cipher() one-shot API are vulnerable. The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as AES-OCB is outside the OpenSSL FIPS module boundary.

The record classifies CVE-2026-45445 under weakness class [CWE-325](https://cwe.mitre.org/data/definitions/325.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 140 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **EPSS (FIRST):** 0.7% probability of exploitation in the next 30 days, higher than 51.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-09, last modified 2026-06-10

## Is CVE-2026-45445 being exploited?

It currently carries a trending score of 18 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [OpenSSL](https://intel.threadlinqs.com/vendors/openssl): OpenSSL

## How to fix CVE-2026-45445

No vendor patch reference has been recorded for CVE-2026-45445 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-45445

1 tracked threat in the Threadlinqs corpus references CVE-2026-45445, either in the campaign’s CVE list or as an indicator on the campaign record.

- [HollowByte: OpenSSL Pre-Authentication TLS DoS Flaw Bloats Server Memory With 11-Byte Payload](https://intel.threadlinqs.com/threat/TL-2026-1457) — MEDIUM · 2026-07-17

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10.

**Vendor advisory and patch**

- [openssl-library.org — vendor advisory](https://openssl-library.org/news/secadv/20260609.txt)
- [github.com — patch](https://github.com/openssl/openssl/commit/843c9b94ca9c2ed248bb30127bb4f3d7af0d607c)
- [github.com — patch (787a6dfba81b7b09c1e05ab31396c0cd7c36b3f7)](https://github.com/openssl/openssl/commit/787a6dfba81b7b09c1e05ab31396c0cd7c36b3f7)
- [github.com — patch (983d54b5cce8d16147548ed1a37892d1720bbab6)](https://github.com/openssl/openssl/commit/983d54b5cce8d16147548ed1a37892d1720bbab6)
- [github.com — patch (7ac4715234ee72d9f3c93426a2c08554b5b771af)](https://github.com/openssl/openssl/commit/7ac4715234ee72d9f3c93426a2c08554b5b771af)

_Showing 5 of 6 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-45445
Full detection coverage and IOCs for threats exploiting CVE-2026-45445 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp