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No exploitation reportedFix available

CVE-2021-3711

No exploitation reported by the sources we read.

  • Published2021-08-24
  • WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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).

Timeline

dates in UTC
  1. 2021-08-2415:15CVE publishedNVD
  2. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-3711?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-3711?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Oracle peoplesoft enterprise peopletools
BranchAffectedFixed in
8.57= 8.57no fix published
8.58= 8.58no fix published
8.59= 8.59no fix published
Debian debian linux
BranchAffectedFixed in
10.0= 10.0no fix published
11.0= 11.0no fix published
Oracle communications session border controller
BranchAffectedFixed in
8.4= 8.4no fix published
9.0= 9.0no fix published

29 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • ICSA-25-226-21 CISA1 known affected

    Siemens BFCClient

    BFCClient

  • ICSA-23-143-02 CISA8 known affected

    Hitachi Energy's RTU500 Series Product (UPDATE B)

    RTU500 series CMU Firmware: >=12.0.1|<=12.0.15 · RTU500 series CMU Firmware: >=12.2.1|<=12.2.12 · RTU500 series CMU Firmware: >=12.4.1|<=12.4.12 · +5 more

Full record on NVD

Fix

  1. Vendor fix CISA ICSA-25-226-21 · 1 productUpdate to V2.17 or later version. Contact customer support to obtain the update
  2. Vendor fix CISA ICSA-23-143-02 · 8 productsRTU500 series CMU Firmware version 12.0.1 - 12.0.14: Update to CMU Firmware version 12.0.15* (Planned Update)
  3. Vendor fix CISA ICSA-23-143-02 · 8 productsRTU500 series CMU Firmware version 12.2.1 - 12.2.11: Update to CMU Firmware version 12.2.12* (Planned Update)
  4. Vendor fix CISA ICSA-23-143-02 · 8 productsRTU500 series CMU Firmware version 12.4.1 - 12.4.11: Update to CMU Firmware version 12.4.12* (Planned Update)
  5. Vendor fix CISA ICSA-23-143-02 · 8 productsRTU500 series CMU Firmware version 12.6.1 - 12.6.8: Update to CMU Firmware version 12.6.9
  6. Vendor fix CISA ICSA-23-143-02 · 8 productsRTU500 series CMU Firmware version 12.7.1 - 12.7.5: Update to CMU Firmware version 12.7.6

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2026-10-08
  • OpenCVESSVC decisionnone—
  • NVDCVSS 3.19.8read 2026-10-23
  • NVDCVSS 2.07.5read 2026-10-23
  • NVDweakness (CWE)CWE-120read 2026-10-23
  • FIRST EPSSEPSS score87.8 %read 2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-08-24
Last Modified
2026-10-08
NVD status
Modified

Frequently asked questions

What is CVE-2021-3711?

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).

Is CVE-2021-3711 actively exploited?

Active exploitation of CVE-2021-3711 has not been confirmed. Its EPSS score was 87.8% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-3711?

CVE-2021-3711 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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