CVE-2021-23840 | Integer overflow in CipherUpdate

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).

Published: 2021-02-16 Last update: 2026-04-16 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2021-23840 is rated High Risk (69.6/100): CVSS High severity, with high exploitation likelihood (EPSS 49.80%, 99th percentile). Core evidence: EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +49.33% over the last day, indicating growing attacker interest. Mandatory action: High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-23840

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.46% 49.80% +49.33%
2 2026-06-03 0.63% 0.46% -0.17%
3 2026-05-25 0.63%

Full EPSS history (75 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-23840

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-23840

GitHub Security Advisory for CVE-2021-23840

OS Trackers for CVE-2021-23840

vendor priority summary link
alpine CVE-2021-23840: 3 source package rows (openssl, openssl1.1-compat, openssl3); 45 state rows across 13 repos (3.10-main, 3.11-main, 3.12-main, 3.17-community, 3.17-main, 3.18-community, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-community, edge-main); fixed 15, open 30. https://security.alpinelinux.org/vuln/CVE-2021-23840
debian not yet assigned CVE-2021-23840 not yet assigned priority: Debian including 1 source packages (openssl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-23840
gentoo normal CVE-2021-23840: 1 GLSA(s) (202103-03), 1 atom(s) (dev-libs/openssl); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-23840
redhat medium https://access.redhat.com/security/cve/CVE-2021-23840
suse medium CVE-2021-23840 severity moderate: SUSE including 648 source package names (0.1.0:libopenssl1_1-1.1.0i-14.15.1, 0.1.75:libopenssl1_1-1.1.0i-14.15.1, …), 1490 product×package rows across 282 product lines (Container bci/bci-init, Container bci/dotnet-aspnet, … (282 product lines)): Fixed 1163, Known Not Affected 191, Known Affected 135, Will Not Fix 1. https://www.suse.com/security/cve/CVE-2021-23840/
ubuntu low CVE-2021-23840 low priority: Ubuntu including 4 source packages (edk2, nodejs, openssl, openssl1.0), 64 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 24, released 20, DNE 15, needed 2, needs-triage 2, ignored 1. https://ubuntu.com/security/CVE-2021-23840

Affected software / configurations for CVE-2021-23840

Vendor Product Version Raw CPE
openssl openssl >= 1.0.2, < 1.0.2y cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
openssl openssl >= 1.1.1, < 1.1.1j cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
tenable log_correlation_engine < 6.0.8 cpe:2.3:a:tenable:log_correlation_engine:*:*:*:*:*:*:*:*
tenable nessus_network_monitor 5.11.0 cpe:2.3:a:tenable:nessus_network_monitor:5.11.0:*:*:*:*:*:*:*
tenable nessus_network_monitor 5.11.1 cpe:2.3:a:tenable:nessus_network_monitor:5.11.1:*:*:*:*:*:*:*
tenable nessus_network_monitor 5.12.0 cpe:2.3:a:tenable:nessus_network_monitor:5.12.0:*:*:*:*:*:*:*
tenable nessus_network_monitor 5.12.1 cpe:2.3:a:tenable:nessus_network_monitor:5.12.1:*:*:*:*:*:*:*
tenable nessus_network_monitor 5.13.0 cpe:2.3:a:tenable:nessus_network_monitor:5.13.0:*:*:*:*:*:*:*
oracle business_intelligence 5.5.0.0.0 cpe:2.3:a:oracle:business_intelligence:5.5.0.0.0:*:*:*:enterprise:*:*:*
oracle business_intelligence 5.9.0.0.0 cpe:2.3:a:oracle:business_intelligence:5.9.0.0.0:*:*:*:enterprise:*:*:*
oracle business_intelligence 12.2.1.3.0 cpe:2.3:a:oracle:business_intelligence:12.2.1.3.0:*:*:*:enterprise:*:*:*
oracle business_intelligence 12.2.1.4.0 cpe:2.3:a:oracle:business_intelligence:12.2.1.4.0:*:*:*:enterprise:*:*:*
oracle communications_cloud_native_core_policy 1.15.0 cpe:2.3:a:oracle:communications_cloud_native_core_policy:1.15.0:*:*:*:*:*:*:*
oracle enterprise_manager_for_storage_management 13.4.0.0 cpe:2.3:a:oracle:enterprise_manager_for_storage_management:13.4.0.0:*:*:*:*:*:*:*
oracle enterprise_manager_ops_center 12.4.0.0 cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*
oracle graalvm 19.3.5 cpe:2.3:a:oracle:graalvm:19.3.5:*:*:*:enterprise:*:*:*
oracle graalvm 20.3.1.2 cpe:2.3:a:oracle:graalvm:20.3.1.2:*:*:*:enterprise:*:*:*
oracle graalvm 21.0.0.2 cpe:2.3:a:oracle:graalvm:21.0.0.2:*:*:*:enterprise:*:*:*
oracle jd_edwards_enterpriseone_tools < 9.2.6.0 cpe:2.3:a:oracle:jd_edwards_enterpriseone_tools:*:*:*:*:*:*:*:*
oracle jd_edwards_world_security a9.4 cpe:2.3:a:oracle:jd_edwards_world_security:a9.4:*:*:*:*:*:*:*
oracle mysql_server < 5.7.33 cpe:2.3:a:oracle:mysql_server:*:*:*:*:*:*:*:*
oracle mysql_server >= 8.0.15, < 8.0.23 cpe:2.3:a:oracle:mysql_server:*:*:*:*:*:*:*:*
oracle nosql_database < 20.3 cpe:2.3:a:oracle:nosql_database:*:*:*:*:*:*:*:*
mcafee epolicy_orchestrator < 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:*:*:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:-:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_1:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_10:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_2:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_3:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_4:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_5:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_6:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_7:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_8:*:*:*:*:*:*
mcafee epolicy_orchestrator 5.10.0 cpe:2.3:a:mcafee:epolicy_orchestrator:5.10.0:update_9:*:*:*:*:*:*
fujitsu m10-1_firmware < xcp2410 cpe:2.3:o:fujitsu:m10-1_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4_firmware < xcp2410 cpe:2.3:o:fujitsu:m10-4_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4s_firmware < xcp2410 cpe:2.3:o:fujitsu:m10-4s_firmware:*:*:*:*:*:*:*:*
fujitsu m12-1_firmware < xcp2410 cpe:2.3:o:fujitsu:m12-1_firmware:*:*:*:*:*:*:*:*
fujitsu m12-2_firmware < xcp2410 cpe:2.3:o:fujitsu:m12-2_firmware:*:*:*:*:*:*:*:*
fujitsu m12-2s_firmware < xcp2410 cpe:2.3:o:fujitsu:m12-2s_firmware:*:*:*:*:*:*:*:*
fujitsu m10-1_firmware < xcp3110 cpe:2.3:o:fujitsu:m10-1_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4_firmware < xcp3110 cpe:2.3:o:fujitsu:m10-4_firmware:*:*:*:*:*:*:*:*
fujitsu m10-4s_firmware < xcp3110 cpe:2.3:o:fujitsu:m10-4s_firmware:*:*:*:*:*:*:*:*
fujitsu m12-1_firmware < xcp3110 cpe:2.3:o:fujitsu:m12-1_firmware:*:*:*:*:*:*:*:*
fujitsu m12-2_firmware < xcp3110 cpe:2.3:o:fujitsu:m12-2_firmware:*:*:*:*:*:*:*:*
fujitsu m12-2s_firmware < xcp3110 cpe:2.3:o:fujitsu:m12-2s_firmware:*:*:*:*:*:*:*:*
nodejs node.js >= 10.0.0, <= 10.12.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
nodejs node.js >= 10.13.0, < 10.24.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:lts:*:*:*
nodejs node.js >= 12.0.0, <= 12.12.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
nodejs node.js >= 12.13.0, < 12.21.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:lts:*:*:*
nodejs node.js >= 14.0.0, <= 14.14.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
nodejs node.js >= 15.0.0, < 15.10.0 cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
nodejs node.js 14.15.0 cpe:2.3:a:nodejs:node.js:14.15.0:*:*:*:lts:*:*:*

References for CVE-2021-23840

URL Tags
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf Third 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/SA44846 Third Party Advisory
https://kc.mcafee.com/corporate/index?page=content&id=SB10366 Third 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/202103-03 Third 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-4855 Third Party Advisory
https://www.openssl.org/news/secadv/20210216.txt Vendor Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpuApr2021.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Patch Third Party Advisory
https://www.tenable.com/security/tns-2021-03 Third Party Advisory
https://www.tenable.com/security/tns-2021-09 Third Party Advisory
https://www.tenable.com/security/tns-2021-10 Third Party Advisory
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