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Vulnerability record · CVE-2017-1000257 · published 31 October 2017

CVE-2017-1000257: Haxx libcurl memory buffer overflow vulnerability

Haxx · Libcurl

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.

9.1 CVSS 3.1 Critical EPSS 6.2% · top 6.7% CWE-119 · Memory buffer overflow
9.1CVSS 3.1 base score, v2 6.4
6.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
16References
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.debian.org/security/2017/dsa-4007 Third Party Advisory
http://www.securityfocus.com/bid/101519 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1039644 Third Party AdvisoryVDB Entry
https://access.redhat.com/errata/RHSA-2017:3263
https://access.redhat.com/errata/RHSA-2018:2486
https://access.redhat.com/errata/RHSA-2018:3558
https://curl.haxx.se/docs/adv_20171023.html Vendor Advisory
https://security.gentoo.org/glsa/201712-04
http://www.debian.org/security/2017/dsa-4007 Third Party Advisory
http://www.securityfocus.com/bid/101519 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1039644 Third Party AdvisoryVDB Entry
https://access.redhat.com/errata/RHSA-2017:3263
https://access.redhat.com/errata/RHSA-2018:2486
https://access.redhat.com/errata/RHSA-2018:3558
https://curl.haxx.se/docs/adv_20171023.html Vendor Advisory
https://security.gentoo.org/glsa/201712-04

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Source: NIST National Vulnerability Database (record CVE-2017-1000257), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.