How severe is CVE-2019-16239?

CVE-2019-16239 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2019-16239 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-16239?

CVE-2019-16239 primarily affects Infradead Openconnect. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-16239?

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

When was CVE-2019-16239 published?

CVE-2019-16239 was published on 2019-09-17 and last updated on 2026-06-17.

CVE-2019-16239

CVE-2019-16239 is a critical-severity vulnerability in Infradead Openconnect with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (88th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Infradead Openconnect
Published: 2019-09-17
Last modified: 2026-06-17

Description

process_http_response in OpenConnect before 8.05 has a Buffer Overflow when a malicious server uses HTTP chunked encoding with crafted chunk sizes.

Frequently asked questions

What is CVE-2019-16239?: process_http_response in OpenConnect before 8.05 has a Buffer Overflow when a malicious server uses HTTP chunked encoding with crafted chunk sizes.
How severe is CVE-2019-16239?: CVE-2019-16239 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2019-16239 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-16239?: CVE-2019-16239 primarily affects Infradead Openconnect. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-16239?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2019-16239 published?: CVE-2019-16239 was published on 2019-09-17 and last updated on 2026-06-17.

References

Affected products (10)

cpe:2.3:a:infradead:openconnect:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:29:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:opensuse:leap:15.0:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*

More vulnerabilities in Infradead Openconnect

CVE-2020-12823 — Critical (CVSS 9.8): OpenConnect 8.09 has a buffer overflow, causing a denial of service (application crash) or possibly unspecified other…
CVE-2013-7098 — Critical (CVSS 9.8): OpenConnect VPN client with GnuTLS before 5.02 contains a heap overflow if MTU is increased on reconnection.
CVE-2012-3291 — High (CVSS 7.8): Heap-based buffer overflow in OpenConnect 3.18 allows remote servers to cause a denial of service via a crafted…
CVE-2010-3901 — Medium (CVSS 6.4): OpenConnect before 2.25 does not properly validate X.509 certificates, which allows man-in-the-middle attackers to…
CVE-2020-12105 — Medium (CVSS 5.9): OpenConnect through 8.08 mishandles negative return values from X509_check_ function calls, which might assist…
CVE-2012-6128 — Medium (CVSS 5.0): Multiple stack-based buffer overflows in http.c in OpenConnect before 4.08 allow remote VPN gateways to cause a denial…

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