CVE-2026-34183

Description

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.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0051

Probability of exploitation

0.40%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-1325 CWE-1325

Affected Products

Vendor	Product	Versions
openssl	openssl	3.4.0 — 3.4.6
openssl	openssl	3.5.0 — 3.5.7
openssl	openssl	3.6.0 — 3.6.3
openssl	openssl	All

References

Advisories & Patches

https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517 https://github.com/openssl/openssl/commit/7d06955ebe0ecf8adfd4c1e92018586da47ef9ac https://github.com/openssl/openssl/commit/d2e9efbe4900a373227deb136e8665401404ffac https://github.com/openssl/openssl/commit/fbaa83859c01ad64f497b757aaf51be7d05ed9eb https://openssl-library.org/news/secadv/20260609.txt

Frequently Asked Questions

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-34183? +

CVE-2026-34183 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0051, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-34183? +

CVE-2026-34183 affects products from openssl, specifically: openssl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-34183? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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