HOME VULNERABILITIESCVE-2021-23840

HIGH

CVE-2021-23840

CWE-190Published: February 16, 2021· Updated: Jun 17, 2026

7.5

CVSS v3.1

Official 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).

Technical Analysis

CVE-2021-23840 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges Req.None

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Debian1 product(s)

debian linux

fujitsu12 product(s)

m10-1 firmwarem10-1m10-4 firmwarem10-4m10-4s firmwarem10-4sm12-1 firmwarem12-1m12-2 firmwarem12-2m12-2s firmwarem12-2s

mcafee1 product(s)

epolicy orchestrator

Node.js1 product(s)

node.js

OpenSSL1 product(s)

openssl

Oracle9 product(s)

business intelligencecommunications cloud native core policyenterprise manager for storage managemententerprise manager ops centergraalvmjd edwards enterpriseone toolsjd edwards world securitymysql servernosql database

tenable2 product(s)

log correlation enginenessus network monitor

Source: NVD CPE · 38 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time

Offensive Security exploit database

GitHub PoC Search

Community PoC repositories

Rapid7 / Metasploit

Metasploit module search

Security advisories & exploits

Official NIST entry

CVE Program entry

External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://www.oracle.com//security-alerts/cpujul2021.html

PATCHhttps://www.oracle.com/security-alerts/cpuApr2021.html

PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html

PATCHhttps://www.oracle.com/security-alerts/cpujan2022.html

PATCHhttps://www.oracle.com/security-alerts/cpuoct2021.html

PATCHhttps://www.oracle.com//security-alerts/cpujul2021.html

PATCHhttps://www.oracle.com/security-alerts/cpuApr2021.html

PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html

PATCHhttps://www.oracle.com/security-alerts/cpujan2022.html

PATCHhttps://www.oracle.com/security-alerts/cpuoct2021.html

ADVISORYhttps://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf

ADVISORYhttps://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44846

ADVISORYhttps://kc.mcafee.com/corporate/index?page=content&id=SB10366

ADVISORYhttps://security.gentoo.org/glsa/202103-03

ADVISORYhttps://security.netapp.com/advisory/ntap-20210219-0009/

ADVISORYhttps://www.debian.org/security/2021/dsa-4855

ADVISORYhttps://www.openssl.org/news/secadv/20210216.txt

ADVISORYhttps://www.tenable.com/security/tns-2021-03

ADVISORYhttps://www.tenable.com/security/tns-2021-09

ADVISORYhttps://www.tenable.com/security/tns-2021-10

ADVISORYhttps://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf

ADVISORYhttps://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44846

ADVISORYhttps://kc.mcafee.com/corporate/index?page=content&id=SB10366

ADVISORYhttps://security.gentoo.org/glsa/202103-03

ADVISORYhttps://security.netapp.com/advisory/ntap-20210219-0009/

ADVISORYhttps://www.debian.org/security/2021/dsa-4855

ADVISORYhttps://www.openssl.org/news/secadv/20210216.txt

ADVISORYhttps://www.tenable.com/security/tns-2021-03

ADVISORYhttps://www.tenable.com/security/tns-2021-09

ADVISORYhttps://www.tenable.com/security/tns-2021-10

All References (40)

→

https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdfThird Party Advisory

→

https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=6a51b9e1d0cf0bf8515f7201b68fb0a3482b3dc1

→

https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=9b1129239f3ebb1d1c98ce9ed41d5c9476c47cb2

→

https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44846Third Party Advisory

→

https://kc.mcafee.com/corporate/index?page=content&id=SB10366Third Party Advisory

→

https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E

→

https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E

→

https://security.gentoo.org/glsa/202103-03Third Party Advisory

→

https://security.netapp.com/advisory/ntap-20210219-0009/Third Party Advisory

→

https://security.netapp.com/advisory/ntap-20240621-0006/

→

https://www.debian.org/security/2021/dsa-4855Third Party Advisory

→

https://www.openssl.org/news/secadv/20210216.txtVendor Advisory

→

https://www.oracle.com//security-alerts/cpujul2021.htmlPatch · Third Party Advisory

→

https://www.oracle.com/security-alerts/cpuApr2021.htmlPatch · Third Party Advisory

→

https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch · Third Party Advisory

Quick Facts

CVE IDCVE-2021-23840

CVSS Score7.5 / 10

SeverityHIGH

WeaknessCWE-190

CISA KEVNo

Affected7 vendor(s)

PublishedFeb 16, 2021

Related CVEs (CWE-190)

Recommended Actions

→Apply vendor patches immediately
→Monitor CVE-2021-23840 in threat intel feeds
→Review IDS/IPS signatures for exploitation attempts

Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.

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