--- title: "CVE-2021-23840: Integer overflow in CipherUpdate | CubePath" description: "Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate may overflow the output length argument in some cases where the input length is close…" language: en source: https://cubepath.com/security/cve/CVE-2021-23840 --- # CVE-2021-23840: Integer overflow in CipherUpdate | CubePath ## Description Calls to EVP\_CipherUpdate, EVP\_EncryptUpdate and EVP\_DecryptUpdate may overflow the output length argument in some cases where the input length is close to the maximum permissable length for an integer on the platform. In such cases the return value from the function call will be 1 (indicating success), but the output length value will be negative. This could cause applications to behave incorrectly or crash. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x). Official description from the CVE record, published by openssl. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-23840) ## Key data ### CVSS 3.1 High 7.5 Score published by CISA-ADP in the CVE record. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | Metric | Value | What it means | | ---------------------- | --------- | ----------------------------------------------------------------------------------- | | Attack vector | Network | The vulnerable component can be reached over a network, possibly from the Internet. | | Attack complexity | Low | No special conditions are needed. The attack can be repeated at will. | | Privileges required | None | No account or privileges are needed. | | User interaction | None | No action from any user is needed. | | Scope | Unchanged | The impact stays within the vulnerable component. | | Confidentiality impact | None | No effect on the secrecy of data. | | Integrity impact | None | No effect on the trustworthiness of data. | | Availability impact | High | Serious or total effect on availability. | CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at [first.org/cvss](https://www.first.org/cvss/) . ### EPSS Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days. Score 0.50732 (50.7% probability) Percentile 98.9% Scores of Nov 10, 2026 Model v2026.06.15 ### CISA assessment as of Apr 16, 2026 Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA. Automatable yes Technical impact partial ### Weakness (CWE) CWE catalog version 5.0. CWE names: Copyright © 2006-2026, The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CWE license. - [CWE-190](https://cwe.mitre.org/data/definitions/190.html) Integer Overflow or Wraparound ## Affected products Products listed in the CVE record, as the CNA published them. - OpenSSL - affected: Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i) - affected: Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x) ## References Links listed in the CVE record. They lead to other sites, which CubePath does not control. - [openssl.org/news/secadv/20210216.txt](https://www.openssl.org/news/secadv/20210216.txt) - [git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=6a…](https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=6a51b9e1d0cf0bf8515f7201b68fb0a3482b3dc1) - [git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=9b…](https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=9b1129239f3ebb1d1c98ce9ed41d5c9476c47cb2) - [DSA-4855](https://www.debian.org/security/2021/dsa-4855) (debian.org) vendor-advisory - [GLSA-202103-03](https://security.gentoo.org/glsa/202103-03) (security.gentoo.org) vendor-advisory - [oracle.com/security-alerts/cpuApr2021.html](https://www.oracle.com/security-alerts/cpuApr2021.html) - [tenable.com/security/tns-2021-10](https://www.tenable.com/security/tns-2021-10) - [tenable.com/security/tns-2021-09](https://www.tenable.com/security/tns-2021-09) - [security.netapp.com/advisory/ntap-20210219-0009](https://security.netapp.com/advisory/ntap-20210219-0009/) - [tenable.com/security/tns-2021-03](https://www.tenable.com/security/tns-2021-03) - [\[bookkeeper-issues\] 20210628 \[GitHub\] \[bookkeeper\] padma81 opened a new issue #2746: Security Vulnerabilities in CentOS 7 image, Upgrade image to CentOS 8](https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E) (lists.apache.org) mailing-list - [\[bookkeeper-issues\] 20210629 \[GitHub\] \[bookkeeper\] padma81 opened a new issue #2746: Security Vulnerabilities in CentOS 7 image, Upgrade image to CentOS 8](https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E) (lists.apache.org) mailing-list - [oracle.com//security-alerts/cpujul2021.html](https://www.oracle.com//security-alerts/cpujul2021.html) - [kb.pulsesecure.net/articles/Pulse\_Security\_Advisories/SA448…](https://kb.pulsesecure.net/articles/Pulse%5FSecurity%5FAdvisories/SA44846) - [oracle.com/security-alerts/cpuoct2021.html](https://www.oracle.com/security-alerts/cpuoct2021.html) - [kc.mcafee.com/corporate/index?page=content&id=SB10366](https://kc.mcafee.com/corporate/index?page=content&id=SB10366) - [oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html) - [oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html) - [cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf) - [security.netapp.com/advisory/ntap-20240621-0006](https://security.netapp.com/advisory/ntap-20240621-0006/) ## Timeline 1. ID reserved Jan 12, 2021 2. Record published Feb 16, 2021 3. Record last updated Apr 16, 2026 ## Look up another CVE ## About CubePath CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection. [Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection) Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:04 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)