--- title: "CVE-2009-0025: EVP_VerifyFinal() and DSA_do_verify() return checks" slug: "aa-00925" description: "It is theoretically possible to spoof answers returned from zones whose DNSKEY algorithms are affected by a recently disclosed OpenSSL issue." updated: 2025-03-25T20:43:36Z published: 2025-03-25T20:43:36Z canonical: "kb.isc.org/aa-00925" --- > ## Documentation Index > Fetch the complete documentation index at: https://kb.isc.org/llms.txt > Use this file to discover all available pages before exploring further. # CVE-2009-0025: EVP_VerifyFinal() and DSA_do_verify() return checks Return values from OpenSSL library functions EVP_VerifyFinal() and DSA_do_verify() were not checked properly CVE: [CVE-2009-0025](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0025) Posting date: 05 Jan 2009 Program Impacted: [BIND](https://www.isc.org/software/bind) Versions affected: 9.0 (all versions), 9.1 (all versions), 9.2 (all versions), 9.3.0, 9.3.1, 9.3.2, 9.3.3, 9.3.4, 9.3.5, 9.3.6, 9.4.0, 9.4.1, 9.4.2, 9.4.3, 9.5.0, 9.5.1, 9.6.0 Severity: Low Exploitable: Remotely **Description:** Note: the 28 July 2009 DDNS DoS attack vulnerability announcement is [here](https://kb.isc.org/docs/aa-00926). Some emails were sent with an incorrect URL reference. We apologize for the confusion. OpenSSL security advisory [CVE-2008-5077](https://www.cve.org/CVERecord?id=CVE-2008-5077) may affect BIND users. The OpenSSL advisory says: > Several functions inside OpenSSL incorrectly checked the result after calling the `EVP_VerifyFinal` function, allowing a malformed signature to be treated as a good signature rather than as an error. This issue affected the signature checks on DSA and ECDSA keys used with SSL/TLS. It is theoretically possible to spoof answers returned from zones whose DNSKEY algorithms are affected by that OpenSSL issue. **Impact:** **Workarounds:** BIND 9.3, 9.4, 9.5 and 9.6: > Disable the affected algorithms in named.conf. This will cause answers from zones signed only with DSA (3) and/or NSEC3DSA (6) to be treated as insecure. BIND 9.3, 9.4, 9.5: disable-algorithms . { DSA; }; BIND 9.6: disable-algorithms . { DSA; NSEC3DSA; }; **Active exploits:** None known at this time. **Solution:** Upgrade OpenSSL to at least OpenSSL 0.9.8j, then upgrade BIND to 9.3.6-P1, 9.4.3-P1, 9.5.1-P1, 9.6.0-P1, which use the updated OpenSSL interface correctly. There are no fixes planned for BIND 9.1 or BIND 9.2, as those releases do not implement the current DNSSEC protocol. Questions should be addressed to [bind9-bugs@isc.org](mailto:bind9-bugs@isc.org). Also see [CVE-2008-5077](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5077) for the corresponding OpenSSL issue **Acknowledgements:** Google Security Team. **Document Revision History:** 2009-01-05 Initial pre-release text 2009-01-07 Public release with corrected CVE 2009-01-23 Solution revised **Related Documents:** See our [BIND Security Matrix](https://kb.isc.org/docs/aa-00913) for a complete listing of Security Vulnerabilities and versions affected. If you'd like more information on our Forum or product support please visit [www.isc.org/support](http://www.isc.org/support). **Do you still have questions?** Questions regarding this advisory should go to [security-officer@isc.org](mailto:security-officer@isc.org) **Note:** ISC patches only [currently supported versions](http://www.isc.org/software/bind/versions). When possible we indicate EOL versions affected. **ISC Security Vulnerability Disclosure Policy:** Details of our current security advisory policy and practice can be found here: [https://www.isc.org/security-vulnerability-disclosure-policy](https://www.isc.org/security-vulnerability-disclosure-policy) This Knowledge Base article [https://kb.isc.org/docs/aa-00925](https://kb.isc.org/docs/aa-00925) is the complete and official security advisory document. **Legal Disclaimer:** Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. 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