How severe is GHSA-9763-4f94-gfch?

No CVSS score has been assigned to GHSA-9763-4f94-gfch yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-9763-4f94-gfch?

GHSA-9763-4f94-gfch affects the following packages: github.com/cloudflare/circl (Go). Ecosystems affected: Go.

How do I fix GHSA-9763-4f94-gfch?

Update github.com/cloudflare/circl to 1.3.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9763-4f94-gfch is resolved across your whole dependency graph.

How do I detect GHSA-9763-4f94-gfch in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudflare/circl, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-9763-4f94-gfch if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-9763-4f94-gfch actively exploited in the wild?

No public exploit code has been indexed for GHSA-9763-4f94-gfch yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-9763-4f94-gfch published, and has it been updated?

GHSA-9763-4f94-gfch was published on January 8, 2024 and was last updated on September 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CIRCL's Kyber: timing side-channel (kyberslash2)GHSA-9763-4f94-gfch

Fix: cloudflare/circl@75ef91e

GHSA-9763-4f94-gfch is a security vulnerability in github.com/cloudflare/circl. A fix is available for github.com/cloudflare/circl — see the affected versions and patch details below.

Also known asGO-2024-2453

Published

Jan 8, 2024

Updated

Sep 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 10, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐹github.com/cloudflare/circl

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

On some platforms, when an attacker can time decapsulation of Kyber on forged cipher texts, they could possibly learn (parts of) the secret key.

Does not apply to ephemeral usage, such as when used in the regular way in TLS.

Patches

Patched in 1.3.7.

References

kyberslash.cr.yp.to

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/cloudflare/circl`	all versions	1.3.7`go get github.com/cloudflare/circl@v1.3.7`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudflare/circl, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cloudflare/circl to 1.3.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9763-4f94-gfch is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact On some platforms, when an attacker can time decapsulation of Kyber on forged cipher texts, they could possibly learn (parts of) the secret key. Does not apply to ephemeral usage, such as when used in the regular way in TLS. ### Patches Patched in 1.3.7. ### References - [kyberslash.cr.yp.to](https://kyberslash.cr.yp.to/)

O3 Security · Impact-Aware SCA

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