How severe is CVE-2019-20021?

CVE-2019-20021 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2019-20021 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-20021?

CVE-2019-20021 primarily affects Upx. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-20021?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-20021 published?

CVE-2019-20021 was published on 2019-12-27 and last updated on 2026-06-17.

CVE-2019-20021

CVE-2019-20021 is a medium-severity vulnerability in Upx with a CVSS 3.x base score of 5.5. 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: Medium (CVSS 3.x base score 5.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (62nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-125
Affected product: Upx
Published: 2019-12-27
Last modified: 2026-06-17

Description

A heap-based buffer over-read was discovered in canUnpack in p_mach.cpp in UPX 3.95 via a crafted Mach-O file.

Frequently asked questions

What is CVE-2019-20021?: A heap-based buffer over-read was discovered in canUnpack in p_mach.cpp in UPX 3.95 via a crafted Mach-O file.
How severe is CVE-2019-20021?: CVE-2019-20021 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2019-20021 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-20021?: CVE-2019-20021 primarily affects Upx. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-20021?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-20021 published?: CVE-2019-20021 was published on 2019-12-27 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:upx:upx:3.95:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*

More vulnerabilities in Upx

CVE-2020-27801 — High (CVSS 7.8): A heap-based buffer over-read was discovered in the get_le64 function in bele.h in UPX 4.0.0 via a crafted Mach-O file.
CVE-2020-27800 — High (CVSS 7.8): A heap-based buffer over-read was discovered in the get_le32 function in bele.h in UPX 4.0.0 via a crafted Mach-O file.
CVE-2020-27799 — High (CVSS 7.8): A heap-based buffer over-read was discovered in the acc_ua_get_be32 function in miniacc.h in UPX 4.0.0 via a crafted…
CVE-2020-27796 — High (CVSS 7.8): A heap-based buffer over-read was discovered in the invert_pt_dynamic function in p_lx_elf.cpp in UPX 4.0.0 via a…
CVE-2021-30500 — High (CVSS 7.8): Null pointer dereference was found in upx PackLinuxElf::canUnpack() in p_lx_elf.cpp,in version UPX 4.0.0. That allow…
CVE-2019-14296 — High (CVSS 7.8): canUnpack in p_vmlinx.cpp in UPX 3.95 allows remote attackers to cause a denial of service (SEGV or buffer overflow,…

All CVEs affecting Upx →

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

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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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