Search/CVE-2021-23840
CVE — High

CVE-2021-23840

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…

CVSS v3.1
7.5 HIGH
EPSS
50.7%
probability of exploitation in 30 days
CISA KEV
Not listed
no confirmed exploitation reported
News coverage
0
sources referencing this CVE
Timeline
disclosure → media coverage
Feb 16, 2021
Disclosure — published as a CVE record. · last revised by NVD Apr 16, 2026
Public PoC (1)
Unverified third-party code — review before executing.