# CVE-2026-34183 — OpenSSL

> As of 2026-06-10, CVE-2026-34183 is a HIGH-severity vulnerability in OpenSSL, CVSS v3.1 7.5, EPSS 1.0% (63.2th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-34183, most recently “HollowByte: OpenSSL Pre-Authentication TLS DoS Flaw Bloats Server Memory With 11-Byte Payload”.

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

## What is CVE-2026-34183?

Issue summary: Remote peer may exhaust heap memory of the QUIC server or client by flooding it with packets containing PATH_CHALLENGE frames. Impact summary: A malicious remote peer can cause an unbounded memory allocation which can lead to an abnormal termination of the application acting as a QUIC client or server and a Denial of Service. A remote peer may exhaust heap memory by flooding the local QUIC stack with PATH_CHALLENGE frames. The local QUIC stack allocates a PATH_RESPONSE frame for every PATH_CHALLENGE it receives. The allocated PATH_RESPONSE frame gets freed only when the remote peer acknowledges reception of the PATH_RESPONSE frame which will not be done by a malicious peer. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue. The QUIC stack is outside of OpenSSL FIPS module boundary.

The record classifies CVE-2026-34183 under weakness class [CWE-1325](https://cwe.mitre.org/data/definitions/1325.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 availability. 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:N/I:N/A:H`)
- **EPSS (FIRST):** 1.0% probability of exploitation in the next 30 days, higher than 63.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.3/10 — 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-2026-34183 being exploited?

It currently carries a trending score of 21 in the Threadlinqs vulnerability feed.

## Affected products and versions

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

## How to fix CVE-2026-34183

The record marks a vendor fix as available for CVE-2026-34183. Patch reference: [https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517](https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517). Vendor advisory: [https://openssl-library.org/news/secadv/20260609.txt](https://openssl-library.org/news/secadv/20260609.txt). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-34183

1 tracked threat in the Threadlinqs corpus references CVE-2026-34183, 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, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**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/fbaa83859c01ad64f497b757aaf51be7d05ed9eb)
- [github.com — patch (5b306efb0b3779dfdd0803b4afc9d08c91f11517)](https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517)
- [github.com — patch (7d06955ebe0ecf8adfd4c1e92018586da47ef9ac)](https://github.com/openssl/openssl/commit/7d06955ebe0ecf8adfd4c1e92018586da47ef9ac)
- [github.com — patch (d2e9efbe4900a373227deb136e8665401404ffac)](https://github.com/openssl/openssl/commit/d2e9efbe4900a373227deb136e8665401404ffac)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-34183
Full detection coverage and IOCs for threats exploiting CVE-2026-34183 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp