How severe is CVE-2021-20285?

CVE-2021-20285 has a CVSS 3.x base score of 6.6, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-20285 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20285?

CVE-2021-20285 affects Upx. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-20285?

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

When was CVE-2021-20285 published?

CVE-2021-20285 was published on 2021-03-26 and last updated on 2026-06-17.

CVE-2021-20285

CVE-2021-20285 is a medium-severity vulnerability in Upx with a CVSS 3.x base score of 6.6. 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-787.

Key facts

Severity: Medium (CVSS 3.x base score 6.6)
CVSS v2: 8.3
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Upx
Published: 2021-03-26
Last modified: 2026-06-17

Description

A flaw was found in upx canPack in p_lx_elf.cpp in UPX 3.96. This flaw allows attackers to cause a denial of service (SEGV or buffer overflow and application crash) or possibly have unspecified other impacts via a crafted ELF. The highest threat from this vulnerability is to system availability.

Frequently asked questions

What is CVE-2021-20285?: A flaw was found in upx canPack in p_lx_elf.cpp in UPX 3.96. This flaw allows attackers to cause a denial of service (SEGV or buffer overflow and application crash) or possibly have unspecified other impacts via a crafted ELF. The highest threat from this vulnerability is to system availability.
How severe is CVE-2021-20285?: CVE-2021-20285 has a CVSS 3.x base score of 6.6, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-20285 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20285?: CVE-2021-20285 affects Upx. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-20285?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20285 published?: CVE-2021-20285 was published on 2021-03-26 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:upx:upx:3.96:*:*:*:*:*:*:*

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,…

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