CVE-2018-16840

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2018-10-31 · updated 2026-06-17
Weakness: CWE-416

Description

A heap use-after-free flaw was found in curl versions from 7.59.0 through 7.61.1 in the code related to closing an easy handle. When closing and cleaning up an 'easy' handle in the `Curl_close()` function, the library code first frees a struct (without nulling the pointer) and might then subsequently erroneously write to a struct field within that already freed struct.

Affected products

Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 18.10
curl: from 7.59.0 before 7.62.0 — fixed in 7.62.0

How to fix

Upgrade to a fixed version: curl 7.62.0. Check the vendor advisory for mitigations.

References

http://www.securitytracker.com/id/1042013
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16840
https://curl.haxx.se/docs/CVE-2018-16840.html
https://github.com/curl/curl/commit/81d135d67155c5295b1033679c606165d4e28f3f
https://security.gentoo.org/glsa/201903-03
https://usn.ubuntu.com/3805-1/
http://www.securitytracker.com/id/1042013
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16840
https://curl.haxx.se/docs/CVE-2018-16840.html
https://github.com/curl/curl/commit/81d135d67155c5295b1033679c606165d4e28f3f
https://security.gentoo.org/glsa/201903-03
https://usn.ubuntu.com/3805-1/

Get alerted when CVE-2018-16840 or the next vulnerability affects your stack