# CVE-2026-77696: Timing Side-Channel in SM2 Signature Generation

> Timing side-channel in SM2 signature generation allows attackers to recover private keys by measuring signing times.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2026
- **Updated:** 29 Sep 2026
- **Also known as:** ALPINE-CVE-2026-77696, AZL-105366, AZL-105465, AZL-105489, AZL-105519, AZL-105570, AZL-105603, AZL-105732, AZL-105816, AZL-105861, BELL-CVE-2026-77696, CLEANSTART-2026-XR25689, DEBIAN-CVE-2026-77696, ECHO-07fb-c131-d133, GHSA-9qr7-mmm2-9f2r, MINI-p9qh-pfvw-f9c3, UBUNTU-CVE-2026-77696

## What is CVE-2026-77696?

CVE-2026-77696 is a low-severity vulnerability in Openssl Openssl, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-208 (Observable Timing Discrepancy)

## Which versions are affected by CVE-2026-77696?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-77696?

Apply the vendor's patch.

## Is CVE-2026-77696 being exploited?

There is no known exploitation of CVE-2026-77696 in the wild and no public exploit code.

## Other vulnerabilities in Openssl Openssl

- [CVE-2009-3245](https://insights.sbomify.com/CVE-2009-3245/): Null dereference in n/a (critical 10.0)
- [CVE-2006-3738](https://insights.sbomify.com/CVE-2006-3738/): Memory corruption in n/a (critical 10.0)
- [CVE-2026-63073](https://insights.sbomify.com/CVE-2026-63073/): Untrusted Sender DN Used as Format String in CMP Response Validation (critical 9.8)
- [CVE-2016-6309](https://insights.sbomify.com/CVE-2016-6309/): Use after free in n/a (critical 9.8)
- [CVE-2016-0799](https://insights.sbomify.com/CVE-2016-0799/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77696 and fix it if it is affected.

What it is: CVE-2026-77696 is a low-severity vulnerability in Openssl Openssl, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77696 in the wild and no public exploit code.

Affected product: Openssl Openssl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77696/ (Markdown: https://insights.sbomify.com/CVE-2026-77696/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77696
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77696
- OSV: https://osv.dev/vulnerability/CVE-2026-77696

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77696/
Summaries are generated and may contain mistakes; the official description above is the record.