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CVE-2017-1000257

Critical Vulnerability: CVE-2017-1000257 — haxx, debian — libcurl, debian_linux

An IMAP FETCH response line indicates the size of the returned data, in number of bytes. When that response says the data is zero bytes, libcurl would pass on that (non-existing) data with a pointer and the size (zero) to the deliver-data function. libcurl's deliver-data function treats zero as a magic number and invokes strlen() on the data to figure out the length. The strlen() is called on a heap based buffer that might not be zero terminated so libcurl might read beyond the end of it into wh

Wednesday, April 15, 2026haxx, debianVulnios Threat Intelligence
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Executive Summary

An IMAP FETCH response line indicates the size of the returned data, in number of bytes. When that response says the data is zero bytes, libcurl would pass on that (non-existing) data with a pointer and the size (zero) to the deliver-data function. libcurl's deliver-data function treats zero as a magic number and invokes strlen() on the data to figure out the length. The strlen() is called on a heap based buffer that might not be zero terminated so libcurl might read beyond the end of it into whatever memory lies after (or just crash) and then deliver that to the application as if it was actually downloaded.

Why It Matters

CVE-2017-1000257 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.1/10

EPSS (Exploit Prediction): 1.0% probability of exploitation in the next 30 days.

Affected Technologies

Vendors: haxx, debian

Products: libcurl, debian_linux

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2017-1000257.
  • Apply available patches — Visit vendor advisories for the latest security updates.
  • Monitor for exploitation — Check your SIEM/IDS logs for related indicators.
  • Use Vulnios to continuously monitor your exposure to CVE-2017-1000257 and similar vulnerabilities.

    References & Sources

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    Affected Products

    libcurldebian_linux

    Sources

    critical

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