CVE-2026-77696

Timing Side-Channel in SM2 Signature Generation

Products / packages OpenSSL · Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · 3 more

Published 29/09/2026, 15:32:22 UTC

Severity and exploitation

Not in CISA KEV

KEV coverage does not rule out exploitation.

KEV checked 15/11/2026, 01:05:31 UTC

CISA-ADP · CVSS:3.1 · 3.7

Assessment vector

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

Severity

low3.7

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Fix status not established

No structured fix or guidance is available here. Check the latest publisher advisory.

What this means

Issue summary: SM2 signature generation uses non-constant-time arithmetic on secret values, forming a timing side-channel.

Source excerpt · openssl

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

OpenSSL · openssl

OpenSSL

6 ranges

openssl version evidence

Check a product version

Compare with this publisher’s ranges. This does not inspect your installation.

affected

4.0.0 → before 4.0.3

semver versions

3.6.0 → before 3.6.5

semver versions

3.5.0 → before 3.5.9

semver versions

3.4.0 → before 3.4.8

semver versions

3.0.0 → before 3.0.23

semver versions

V3.1.7 → before *

custom versions

Other versions: unknown

Automatic dependency matching is unavailable for this record. Use the product evidence and publisher’s instructions to check your installation.

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

No structured fix or remediation guidance is available here. Check the full source description and vendor’s latest advisory for a patch or workaround; do not assume another version is safe.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

Issue summary: SM2 signature generation uses non-constant-time arithmetic on secret values, forming a timing side-channel.

Impact summary: An attacker able to measure SM2 signing times may learn information about the per-signature secret nonce, which over many signatures can, via a lattice / Hidden Number Problem attack, lead to recovery of the private key.

CWE: CWE-208: Observable Timing Discrepancy

Description: SM2 signature generation computes the signature value using variable-time BIGNUM operations on the secret nonce and the private key, so the time taken to produce an SM2 signature depends on these secret values, forming a timing side-channel.

Applications performing SM2 signature generation are affected on all platforms.

FIPS Impact: no SM2 is not a FIPS algorithm.

References

6 sources

openssl-library.org/news/secadv/20260929.txt

Vendor advisoryopenssl

openssl/openssl · commit 20b2062

Patchopenssl

openssl/openssl · commit 1c4aed8

Patchopenssl

openssl/openssl · commit 6b90445

Patchopenssl

openssl/openssl · commit 419f5cb

Patchopenssl

cert-portal.siemens.com/productcert/html/ssa-457936.html

Source referencesiemens-SADP

Inside the record

Evidence available

Package identity · not supplied

Version evidence

Remediation guidance · not supplied

Weakness classification

Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-77696

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-208 ↗

CWE-208 Observable Timing Discrepancy

openssl

Contributing organizations · 3

openssl

Assigning organization

2026-09-29

CISA-ADP

Additional data publisher

2026-09-29

siemens-SADP

Additional data publisher

2026-11-10

Timeline

All times UTC

29 Sept 2026, 15:32
Advisory published
Publication date supplied by the source.
10 Nov 2026, 12:49
Source updated
Latest modification date supplied by the source.
10 Nov 2026, 13:03
Last imported by cve.new
Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes

No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.

Reading the signals

Severity · CVSS: Technical impact and attack conditions. The headline is the highest imported catalog score; sources may disagree.
Observed exploitation · KEV: An absent or unavailable KEV listing does not establish that exploitation has not occurred.
Predicted exploitation · EPSS: 0.40% estimated probability in the next 30 days. 2026-11-09 · FIRST EPSS.

CISA-ADP · SSVC

CISA Coordinator · 2026-09-29

Exploitation: none
Automatable: no
Technical Impact: partial

SSVC describes the publisher’s decision context. Your organization’s exposure and priorities may differ.

Record identifiers

Aliases: None recorded

Source evidence

Request a correction or dispute

Start with the assigning organization for this record. Include the CVE ID, the disputed information, and supporting evidence. A dispute does not itself reject a record.

Find the responsible CNA →Official dispute and escalation process ↗

CVE CVE-2026-77696

Enrichment coverage

NVDAvailable

Checked 10/11/2026, 13:10:36 UTC

GHSAAvailable

Checked 10/11/2026, 13:10:36 UTC

EUVDAvailable

Checked 10/11/2026, 13:10:38 UTC

EPSSAvailable

Checked 10/11/2026, 13:10:35 UTC

Additional source evidence

FIRST EPSS · CVE-2026-77696

EPSS 0.40% probability of exploitation in the next 30 days. Percentile: 34.11% · 2026-11-09

Checked 10/11/2026, 13:10:35 UTC

NVD · CVE-2026-77696

CVSS 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Checked 10/11/2026, 13:10:36 UTC

GitHub Advisory Database · GHSA-9qr7-mmm2-9f2r

CVSS 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Checked 10/11/2026, 13:10:36 UTC

ENISA EUVD · EUVD-2026-89012

CVSS 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Checked 10/11/2026, 13:10:38 UTC

Sponsored by MoxsoBuild security habits with adaptive training and phishing simulations.View as JSON

Timing Side-Channel in SM2 Signature Generation

Severity and exploitation

What this means

Attack conditions

Affected versions

OpenSSL

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)

affected

unaffected

unknown

SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)

affected

unaffected

unknown

What to do

Public exploit evidence

Original source description

References

Inside the record

Evidence available

Original records

Underlying weaknesses

Timeline

Advisory published

Source updated

Last imported by cve.new

What changed