CVE-2021-21814

CVE-2021-21814 is a high-severity vulnerability in Att Xmill with a CVSS 3.x base score of 7.8. 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-88.

Key facts

Description

Within the function HandleFileArg the argument filepattern is under control of the user who passes it in from the command line. filepattern is passed directly to strlen to determine the ending location of the char* passed in by the user, no checks are done to see if the passed in char* is longer than the staticly sized buffer data is memcpy‘d into, but after the memcpy a null byte is written to what is assumed to be the end of the buffer to terminate the char*, but without length checks, this null write occurs at an arbitrary offset from the buffer. An attacker can provide malicious input to trigger this vulnerability.

Frequently asked questions

What is CVE-2021-21814?
Within the function HandleFileArg the argument filepattern is under control of the user who passes it in from the command line. filepattern is passed directly to strlen to determine the ending location of the char* passed in by the user, no checks are done to see if the passed in char* is longer than the staticly sized buffer data is memcpy‘d into, but after the memcpy a null byte is written to what is assumed to be the end of the buffer to terminate the char*, but without length checks, this null write occurs at an arbitrary offset from the buffer. An attacker can provide malicious input to trigger this vulnerability.
How severe is CVE-2021-21814?
CVE-2021-21814 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-21814 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21814?
CVE-2021-21814 affects Att Xmill. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21814?
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-2021-21814 published?
CVE-2021-21814 was published on 2021-08-13 and last updated on 2026-06-17.

References

Affected products (1)

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