CVE-2021-23840

libssl3t64: Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate mayoverflow the output length argument in some cas...

CVE-2021-23840 is fixed in 17 products on 1 platform, first by libssl1.0.0 1.0.2n-1ubuntu5.6, released February 16, 2021. It is not reported as exploited. Patch Radar priority: High.

High
CVSS
7.5
Low
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.5073
98th percentile

Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate mayoverflow the output length argument in some cases where the input length isclose to the maximum permissable length for an integer on the platform. Insuch cases the return value from the function call will be 1 (indicatingsuccess), but the output length value will be negative. This could causeapplications to behave incorrectly or crash. OpenSSL versions 1.1.1i andbelow are affected by this issue. Users of these versions should upgrade toOpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by thisissue. However OpenSSL 1.0.2 is out of support and no longer receivingpublic updates. Premium support customers of OpenSSL 1.0.2 should upgradeto 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).

Where it's fixed

ProductFixed inFixReleased
Linux
edk2 · rocky 8 0:20210527gite1999b264f1f-3.el8 RLSA-2021:4198 Nov 9, 2021
edk2-aarch64 · RHEL 8 0:20210527gite1999b264f1f-3.el8 RHSA-2021:4198 Nov 9, 2021
edk2-ovmf · RHEL 8 0:20210527gite1999b264f1f-3.el8 RHSA-2021:4198 Nov 9, 2021
edk2-ovmf · almalinux 8 20210527gite1999b264f1f-3.el8 ALSA-2021:4198 Nov 9, 2021
libssl1.0.0 · Ubuntu 18.04.6 LTS (bionic) 1.0.2n-1ubuntu5.6 libssl1.0.0 1.0.2n-1ubuntu5.6 Feb 16, 2021
libssl1.1 · Ubuntu 18.04.6 LTS (bionic) 1.1.1-1ubuntu2.1~18.04.8 libssl1.1 1.1.1-1ubuntu2.1~18.04.8 Feb 16, 2021
libssl1.1 · Ubuntu 20.04 LTS (focal) 1.1.1f-1ubuntu2.2 libssl1.1 1.1.1f-1ubuntu2.2 Feb 16, 2021
libssl3t64 · Ubuntu 24.10 (oracular) 1.1.1j-1ubuntu1 libssl3t64 1.1.1j-1ubuntu1 Jan 16, 2026
libssl3t64 · Ubuntu 25.04 (plucky) 1.1.1j-1ubuntu1 libssl3t64 1.1.1j-1ubuntu1 Jan 16, 2026
openssl · RHEL 8 1:1.1.1k-4.el8 RHSA-2021:4424 Nov 9, 2021
openssl · Ubuntu 18.04.6 LTS (bionic) 1.1.1-1ubuntu2.1~18.04.8 openssl 1.1.1-1ubuntu2.1~18.04.8 Feb 16, 2021
openssl · Ubuntu 20.04 LTS (focal) 1.1.1f-1ubuntu2.2 openssl 1.1.1f-1ubuntu2.2 Feb 16, 2021
openssl · Ubuntu 24.10 (oracular) 1.1.1j-1ubuntu1 openssl 1.1.1j-1ubuntu1 Jan 16, 2026
openssl · Ubuntu 25.04 (plucky) 1.1.1j-1ubuntu1 openssl 1.1.1j-1ubuntu1 Jan 16, 2026
openssl · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl · rocky 8 1:1.1.1k-4.el8 RLSA-2021:4424 Nov 9, 2021
openssl-debugsource · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl-devel · RHEL 8 1:1.1.1k-4.el8 RHSA-2021:4424 Nov 9, 2021
openssl-devel · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl-libs · RHEL 8 1:1.1.1k-4.el8 RHSA-2021:4424 Nov 9, 2021
openssl-libs · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl-perl · RHEL 8 1:1.1.1k-4.el8 RHSA-2021:4424 Nov 9, 2021
openssl-perl · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl-static · ol 8 2:1.1.1k-4.ksplice1.el8 ELSA-2021-9561 Nov 23, 2021
openssl1.0 · Ubuntu 18.04.6 LTS (bionic) 1.0.2n-1ubuntu5.6 openssl1.0 1.0.2n-1ubuntu5.6 Feb 16, 2021
ovmf · Ubuntu 20.04 LTS (focal) 0~20191122.bd85bf54-2ubuntu3.3 ovmf 0~20191122.bd85bf54-2ubuntu3.3 Sep 13, 2021
qemu-efi · Ubuntu 20.04 LTS (focal) 0~20191122.bd85bf54-2ubuntu3.3 qemu-efi 0~20191122.bd85bf54-2ubuntu3.3 Sep 13, 2021
qemu-efi-aarch64 · Ubuntu 20.04 LTS (focal) 0~20191122.bd85bf54-2ubuntu3.3 qemu-efi-aarch64 0~20191122.bd85bf54-2ubuntu3.3 Sep 13, 2021
qemu-efi-arm · Ubuntu 20.04 LTS (focal) 0~20191122.bd85bf54-2ubuntu3.3 qemu-efi-arm 0~20191122.bd85bf54-2ubuntu3.3 Sep 13, 2021

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