NVD / CVE Program· CNA openssl

CVE-2021-3711: SM2 Decryption Buffer Overflow

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available

Noroxi assessment

Priority: This week (action score 65/100)

Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
Probability of exploitation in the next 30 days: 87.8% (FIRST EPSS); higher than 99.7% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: openssl (Alpine:v3.11) 1.1.1l-r0; openssl3 (Alpine:v3.15) 1.1.1l-r0; openssl1.1-compat (Alpine:v3.17) 1.1.1l-r0.
Mentioned 6 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Upgrade to openssl (Alpine:v3.11) 1.1.1l-r0; openssl3 (Alpine:v3.15) 1.1.1l-r0; openssl1.1-compat (Alpine:v3.17) 1.1.1l-r0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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).

Published: Aug 24, 2021
Updated: Oct 8, 2026
EPSS: 87.8% · 99th percentile
CWE: CWE-120

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Action score

This week

Don’t wait for the next maintenance window.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 26 / 30 · 87.8%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
Proof of concept exists, no weaponized module
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
openssl	openssl	cpe:2.3:a:openssl:openssl
debian	debian linux	cpe:2.3:o:debian:debian_linux
netapp	active iq unified manager	cpe:2.3:a:netapp:active_iq_unified_manager
netapp	clustered data ontap	cpe:2.3:a:netapp:clustered_data_ontap
netapp	clustered data ontap antivirus connector	cpe:2.3:a:netapp:clustered_data_ontap_antivirus_connector
netapp	e-series santricity os controller	cpe:2.3:a:netapp:e-series_santricity_os_controller
netapp	hci management node	cpe:2.3:a:netapp:hci_management_node
netapp	manageability software development kit	cpe:2.3:a:netapp:manageability_software_development_kit
netapp	oncommand insight	cpe:2.3:a:netapp:oncommand_insight
netapp	oncommand workflow automation	cpe:2.3:a:netapp:oncommand_workflow_automation
netapp	santricity smi-s provider	cpe:2.3:a:netapp:santricity_smi-s_provider
netapp	snapcenter	cpe:2.3:a:netapp:snapcenter

and 19 more

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (openssl). Independent of NVD's CPE analysis and usually ahead of it.

OpenSSL OpenSSL
- Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k)affected

Affected versions · NVD (20)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

debian debian linux10.0
debian debian linux11.0
netapp active iq unified managerall versions
netapp clustered data ontapall versions
netapp clustered data ontap antivirus connectorall versions
netapp e-series santricity os controller11.0 and later · up to 11.50.2 inclusive
netapp hci management nodeall versions
netapp manageability software development kitall versions
netapp oncommand insightall versions
netapp oncommand workflow automationall versions
netapp santricity smi-s providerall versions
netapp snapcenterall versions
netapp solidfireall versions
netapp storage encryptionall versions
openssl openssl1.1.1 and later · before 1.1.1l
oracle communications cloud native core security edge protection proxy1.7.0
oracle communications cloud native core unified data repository1.15.0
oracle communications session border controller8.4
oracle communications session border controller9.0
oracle communications unified session manager8.2.5

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.11	openssl	from 1.1.1 · before 1.1.1l-r0	1.1.1l-r0
Alpine:v3.15	openssl3	before 1.1.1l-r0	1.1.1l-r0
Alpine:v3.17	openssl1.1-compat	before 1.1.1l-r0	1.1.1l-r0
crates.io	openssl-src	from 0.0.0-0 · before 111.16.0	111.16.0
crates.io	openssl-src	before 111.16.0	111.16.0
Debian:10	openssl	before 1.1.1d-0+deb10u7	1.1.1d-0+deb10u7
Debian:11	openssl	before 1.1.1k-1+deb11u1	1.1.1k-1+deb11u1
Debian:12	openssl	before 1.1.1l-1	1.1.1l-1
openSUSE:Leap 15.2	openssl-1_1	before 1.1.1d-lp152.7.21.1	1.1.1d-lp152.7.21.1
openSUSE:Leap 15.3	dracut-saltboot	before 0.1.1665997480.587fa10-150000.1.41.1	0.1.1665997480.587fa10-150000.1.41.1
openSUSE:Leap 15.3	golang-github-boynux-squid_exporter	before 1.6-150000.1.9.1	1.6-150000.1.9.1
openSUSE:Leap 15.3	golang-github-prometheus-promu	before 0.13.0-150000.3.9.1	0.13.0-150000.3.9.1
openSUSE:Leap 15.3	grafana	before 8.5.13-150200.3.29.5	8.5.13-150200.3.29.5
openSUSE:Leap 15.3	grafana	before 8.3.5-150200.3.21.1	8.3.5-150200.3.21.1
openSUSE:Leap 15.3	openssl-1_1	before 1.1.1d-11.27.1	1.1.1d-11.27.1
openSUSE:Leap 15.3	prometheus-postgres_exporter	before 0.10.0-150000.1.3.1	0.10.0-150000.1.3.1
openSUSE:Leap 15.3	rhnlib	before 4.2.6-150000.3.34.1	4.2.6-150000.3.34.1
openSUSE:Leap 15.3	spacecmd	before 4.3.16-150000.3.89.1	4.3.16-150000.3.89.1
openSUSE:Leap 15.3	spacecmd	before 4.2.16-150000.3.77.1	4.2.16-150000.3.77.1
openSUSE:Leap 15.4	prometheus-blackbox_exporter	before 0.19.0-150000.1.14.3	0.19.0-150000.1.14.3
openSUSE:Leap 15.4	wire	before 0.5.0-150000.1.9.3	0.5.0-150000.1.9.3
openSUSE:Tumbleweed	grafana	before 8.3.4-1.1	8.3.4-1.1
openSUSE:Tumbleweed	grype	before 0.92.1-1.1	0.92.1-1.1
SUSE:Enterprise Storage 6	grafana	before 8.5.13-150100.3.12.1	8.5.13-150100.3.12.1

+89

Same product

openssl: all records

Other highest-scoring records for the same primary product.

CVE-2014-0160The (1) TLS and (2) DTLS implementations in OpenSSL 1.0.1 before 1.0.1g do not properly handle Heartbeat Extension packets, which allows…KEV
90Now
CVE-2003-0545Double free vulnerability in OpenSSL 0.9.7 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code…
65This week
CVE-2016-2108The ASN.1 implementation in OpenSSL before 1.0.1o and 1.0.2 before 1.0.2c allows remote attackers to execute arbitrary code or cause a…
62This week

Published before and after this one in the same product

← EarlierCVE-2021-3450Mar 25, 2021 · CA certificate check bypass with X509_V_FLAG_X509_STRICT
35Monitor
← EarlierCVE-2021-3712Aug 24, 2021 · Read buffer overruns processing ASN.1 strings
43Plan
Later →CVE-2021-4044Dec 14, 2021 · Invalid handling of X509_verify_cert() internal errors in libssl
45Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:openssl	1.1.1l-r0 · Alpine:v3.11	Package registry (OSV)
alpine:openssl1.1-compat	1.1.1l-r0 · Alpine:v3.17	Package registry (OSV)
alpine:openssl3	1.1.1l-r0 · Alpine:v3.15	Package registry (OSV)
crates.io:openssl-src	111.16.0	Package registry (OSV)
debian:openssl	1.1.1l-1 · Debian:12	Package registry (OSV)
opensuse:dracut-saltboot	0.1.1665997480.587fa10-150000.1.41.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:golang-github-boynux-squid_exporter	1.6-150000.1.9.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:golang-github-prometheus-promu	0.13.0-150000.3.9.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:grafana	8.3.5-150200.3.21.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:grype	0.92.1-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
opensuse:openssl-1_1	1.1.1d-lp152.7.21.1 · openSUSE:Leap 15.2	Package registry (OSV)
opensuse:prometheus-blackbox_exporter	0.19.0-150000.1.14.3 · openSUSE:Leap 15.4	Package registry (OSV)
opensuse:prometheus-postgres_exporter	0.10.0-150000.1.3.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:rhnlib	4.2.6-150000.3.34.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:spacecmd	4.2.16-150000.3.77.1 · openSUSE:Leap 15.3	Package registry (OSV)
opensuse:wire	0.5.0-150000.1.9.3 · openSUSE:Leap 15.4	Package registry (OSV)
suse:grafana	8.3.5-150000.1.30.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:mgr-cfg	4.2.8-150000.1.24.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:mgr-osad	4.2.8-150000.1.36.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:mgr-push	4.2.5-150000.1.18.2 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:mgr-virtualization	4.2.4-150000.1.26.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:openssl-1_1	1.1.1d-11.27.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2	Package registry (OSV)
suse:prometheus-postgres_exporter	0.10.0-150000.1.3.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:rhnlib	4.2.6-150000.3.34.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:spacecmd	4.2.16-150000.3.77.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:spacewalk-client-tools	4.2.18-150000.3.59.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:spacewalk-koan	4.2.6-150000.3.27.1 · SUSE:Manager Client Tools 15	Package registry (OSV)
suse:spacewalk-oscap	4.2.4-150000.3.18.1 · SUSE:Manager Client Tools 15	Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Proof-of-concept repository on GitHub	stars:0	2026-11-09

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedAug 24, 2021
First PoCNov 9, 2026+1902 d
TodayNov 14, 2026+1907 d

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

John Ouyang

Bug bounty scope

TenableHackerOne · disclosure only (VDP)

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-22-0215 · Mar 11, 2022(Siemens Güvenlik Bildirimi)
TR-21-0989 · Dec 13, 2021(IBM Güvenlik Bildirimi)
TR-21-0921 · Nov 16, 2021(IBM Güvenlik Bülteni Yayınladı)
TR-21-0852 · Oct 20, 2021(Oracle Ürünleri Güvenlik Zafiyeti)
TR-21-0785 · Sep 29, 2021(IBM Güvenlik Bülteni)
TR-21-0740 · Sep 15, 2021(SUSE Linux Enterprise Güncellemesi)

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · variant or chain candidate.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

When data is copied, the source length is not compared with the size of the destination buffer. Excess data overwrites adjacent memory.

The bug in code

The whole CWE-120 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1char buf[256];
2memcpy(buf, pkt->data, pkt->len);

Fixed

1char buf[256];
2if (pkt->len > sizeof(buf)) {
3  return -EINVAL;
4}
5memcpy(buf, pkt->data, pkt->len);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log

Exploit maturitynone → pocNov 10, 2026, 3:36 AM UTC
SSVC exploitation— → noneOct 8, 2026, 11:07 PM UTC
Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

For records you follow, these changes also arrive as notifications. →

References

www.openwall.com/lists/oss-security/2021/08/26/2

Show all references (16 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records