Description
The GnuTLS backend in libcurl 7.21.4 through 7.33.0, when disabling digital signature verification (CURLOPT_SSL_VERIFYPEER), also disables the CURLOPT_SSL_VERIFYHOST check for CN or SAN host name fields, which makes it easier for remote attackers to spoof servers and conduct man-in-the-middle (MITM) attacks.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | curl | 7.34.0-1 | — |
| Debian 13 | curl | 7.34.0-1 | — |
| Debian 12 | curl | 7.34.0-1 | — |
| Debian 7 | curl | 7.26.0-1+wheezy7 | DSA-2824-1 |
Advisories 2
- DSA-2824-1 curl - unchecked tls/ssl certificate host name Debian Security (DSA / DLA) · Mar 9, 2026
- WID-SEC-2023-1655 cURL: Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen BSI CERT-Bund (WID) · Jul 4, 2023
References
- http://curl.haxx.se/docs/adv_20131217.html
- http://www.oracle.com/technetwork/topics/security/cpujul2015-2367936.html
- HPSBMU03112 vendor-advisory
- DSA-2824 vendor-advisory
- USN-2058-1 vendor-advisory