How severe is CVE-2018-20721?

CVE-2018-20721 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-2018-20721 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-20721?

CVE-2018-20721 primarily affects Uriparser Project Uriparser. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-20721?

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-2018-20721 published?

CVE-2018-20721 was published on 2019-01-16 and last updated on 2026-06-17.

CVE-2018-20721

CVE-2018-20721 is a critical-severity vulnerability in Uriparser Project Uriparser 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-125.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (79th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-125
Affected product: Uriparser Project Uriparser
Published: 2019-01-16
Last modified: 2026-06-17

Description

URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.

Frequently asked questions

What is CVE-2018-20721?: URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.
How severe is CVE-2018-20721?: CVE-2018-20721 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-2018-20721 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-20721?: CVE-2018-20721 primarily affects Uriparser Project Uriparser. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-20721?: 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-2018-20721 published?: CVE-2018-20721 was published on 2019-01-16 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:uriparser_project:uriparser:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

More vulnerabilities in Uriparser Project Uriparser

CVE-2018-19199 — Critical (CVSS 9.8): An issue was discovered in uriparser before 0.9.0. UriQuery.c allows an integer overflow via a uriComposeQuery* or…
CVE-2018-19198 — Critical (CVSS 9.8): An issue was discovered in uriparser before 0.9.0. UriQuery.c allows an out-of-bounds write via a uriComposeQuery* or…
CVE-2024-34402 — High (CVSS 8.6): An issue was discovered in uriparser through 0.9.7. ComposeQueryEngine in UriQuery.c has an integer overflow via long…
CVE-2018-19200 — High (CVSS 7.5): An issue was discovered in uriparser before 0.9.0. UriCommon.c allows attempted operations on NULL input via a…
CVE-2024-34403 — Medium (CVSS 5.9): An issue was discovered in uriparser through 0.9.7. ComposeQueryMallocExMm in UriQuery.c has an integer overflow via a…
CVE-2021-46142 — Medium (CVSS 5.5): An issue was discovered in uriparser before 0.9.6. It performs invalid free operations in uriNormalizeSyntax.

All CVEs affecting Uriparser Project Uriparser →

Other CWE-125 (Out-of-bounds Read) vulnerabilities

CVE-2026-24826 — Critical (CVSS 10.0): Out-of-bounds Write, Divide By Zero, NULL Pointer Dereference, Use of Uninitialized Resource, Out-of-bounds Read,…
CVE-2024-22004 — Critical (CVSS 10.0): Due to length check, an attacker with privilege access on a Linux Nonsecure operating system can trigger a…
CVE-2021-41556 — Critical (CVSS 10.0): sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that…
CVE-2021-21777 — Critical (CVSS 10.0): An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer…
CVE-2017-14451 — Critical (CVSS 10.0): An exploitable out-of-bounds read vulnerability exists in libevm (Ethereum Virtual Machine) of CPP-Ethereum. A…
CVE-2013-0767 — Critical (CVSS 10.0): The nsSVGPathElement::GetPathLengthScale function in Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and…

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