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CVE-2021-23840

Severity
HIGH
CVSS
7.5
EPSS
0.50732
Risk score
47.76
CISA KEV
No
PoC
No
Published
2021-02-16
Modified
2026-04-16
First seen
2026-08-07
Aliases
EUVD-2021-1843, GHSA-QGM6-9472-PWQ7
Products
OpenSSL:OpenSSL Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x), OpenSSL:OpenSSL Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i)
Sources
euvd EUVD-2021-1843

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).

References