How severe is CVE-2016-6304?

CVE-2016-6304 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2016-6304 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 63% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-6304?

CVE-2016-6304 primarily affects Openssl. In total, 38 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-6304?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2016-6304 published?

CVE-2016-6304 was published on 2016-09-26 and last updated on 2026-06-17.

CVE-2016-6304

CVE-2016-6304 is a high-severity vulnerability in Openssl with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 63% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-401.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 63% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-401
Affected product: Openssl
Published: 2016-09-26
Last modified: 2026-06-17

Description

Multiple memory leaks in t1_lib.c in OpenSSL before 1.0.1u, 1.0.2 before 1.0.2i, and 1.1.0 before 1.1.0a allow remote attackers to cause a denial of service (memory consumption) via large OCSP Status Request extensions.

Frequently asked questions

What is CVE-2016-6304?: Multiple memory leaks in t1_lib.c in OpenSSL before 1.0.1u, 1.0.2 before 1.0.2i, and 1.1.0 before 1.1.0a allow remote attackers to cause a denial of service (memory consumption) via large OCSP Status Request extensions.
How severe is CVE-2016-6304?: CVE-2016-6304 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2016-6304 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 63% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-6304?: CVE-2016-6304 primarily affects Openssl. In total, 38 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-6304?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2016-6304 published?: CVE-2016-6304 was published on 2016-09-26 and last updated on 2026-06-17.

References

Affected products (38)

cpe:2.3:a:openssl:openssl:1.0.2:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2:beta1:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2:beta2:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2:beta3:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2a:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2b:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2c:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2d:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2e:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2f:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.2h:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.1.0:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1:beta1:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1:beta2:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1:beta3:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1a:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1b:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1c:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1d:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1e:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1f:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1g:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1h:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1i:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1j:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1k:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1l:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1m:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1n:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1o:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1p:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1q:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1r:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1s:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:1.0.1t:*:*:*:*:*:*:*
cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
cpe:2.3:o:novell:suse_linux_enterprise_module_for_web_scripting:12.0:*:*:*:*:*:*:*

More vulnerabilities in Openssl

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CVE-2021-3711 — Critical (CVSS 9.8): In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt().…
CVE-2016-6309 — Critical (CVSS 9.8): statem/statem.c in OpenSSL 1.1.0a does not consider memory-block movement after a realloc call, which allows remote…

All CVEs affecting Openssl →

Other CWE-401 (Missing Release of Memory after Effective Lifetime) vulnerabilities

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CVE-2024-25450 — High (CVSS 8.8): imlib2 v1.9.1 was discovered to mishandle memory allocation in the function init_imlib_fonts().
CVE-2023-33718 — High (CVSS 8.8): mp4v2 v2.1.3 was discovered to contain a memory leak via MP4File::ReadString() at mp4file_io.cpp
CVE-2021-40633 — High (CVSS 8.8): A memory leak (out-of-memory) in gif2rgb in util/gif2rgb.c in giflib 5.1.4 allows remote attackers trigger an out of…
CVE-2021-3492 — High (CVSS 8.8): Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring…
CVE-2019-17340 — High (CVSS 8.8): An issue was discovered in Xen through 4.11.x allowing x86 guest OS users to cause a denial of service or gain…

Browse all CWE-401 (Missing Release of Memory after Effective Lifetime) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

218.4.91.163 (ipv4-addr)
200.77.172.159 (ipv4-addr)
200.196.50.91 (ipv4-addr)
166.62.41.190 (ipv4-addr)
50.62.22.47 (ipv4-addr)
191.101.33.225 (ipv4-addr)
111.68.102.19 (ipv4-addr)
122.3.106.113 (ipv4-addr)