CVE-2021-3711

high
Published 2021-08-24 · Modified 2023-11-08
CVSS v3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2
VIR risk
8.0

Description

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

Predictions

Exploit likelihood
30%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-3711

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-3711.html

OS impact

OSVersionStatusFixed in
arch archfixed1:1.1.1.l-1
suse slesaffected
debian debianbookwormfixed1.1.1l-1
debian debianbullseyefixed1.1.1k-1+deb11u1
debian debianforkyfixed1.1.1l-1
debian debiansidfixed1.1.1l-1
debian debiantrixiefixed1.1.1l-1

Package impact

EcosystemPackageVulnerableFixed
rust crates.ioopenssl-src
rust crates.ioopenssl-src<111.16.0111.16.0
rust crates.ioopenssl-src>=0.0.0-0,<111.16.0111.16.0

References

Verify integrity in audit chain (admin only). AS-IS.