How severe is GHSA-hc3c-63hc-2r9f?

No CVSS score has been assigned to GHSA-hc3c-63hc-2r9f yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-hc3c-63hc-2r9f?

GHSA-hc3c-63hc-2r9f affects the following packages: libcrux-chacha20poly1305 (crates.io). Ecosystems affected: crates.io.

How do I fix GHSA-hc3c-63hc-2r9f?

Update libcrux-chacha20poly1305 to 0.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hc3c-63hc-2r9f is resolved across your whole dependency graph.

How do I detect GHSA-hc3c-63hc-2r9f in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for libcrux-chacha20poly1305, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-hc3c-63hc-2r9f 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-hc3c-63hc-2r9f actively exploited in the wild?

No public exploit code has been indexed for GHSA-hc3c-63hc-2r9f 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-hc3c-63hc-2r9f published, and has it been updated?

GHSA-hc3c-63hc-2r9f was published on May 19, 2026 and was last updated on May 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

Not in CISA KEV

GHSA-hc3c-63hc-2r9f — libcrux-chacha20poly1305

Fix: cryspen/libcrux#1386

GHSA-hc3c-63hc-2r9f is a security vulnerability in libcrux-chacha20poly1305. A fix is available for libcrux-chacha20poly1305 — see the affected versions and patch details below.

libcrux: Potential Panic on Overlong Ciphertext Buffer

Also known asRUSTSEC-2026-0124

Published

May 19, 2026

Updated

May 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of May 20, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🦀libcrux-chacha20poly1305

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

Description

An application that passes in a ciphertext buffer of length greater than ptxt.len() + TAG_LEN to libcrux_chacha20poly1305::encrypt or libcrux_chacha20poly1305::xchacha20_poly1305::encrypt would experience a panic.

Impact

An application where the length of the ciphertext buffer is under attacker control could be made to crash.

Mitigation

The fix makes it so that libcrux_chacha20poly1305::encrypt and libcrux_chacha20poly1305::xchacha20_poly1305::encrypt no longer panic in this case, but instead write out the ciphertext and tag into the first ptxt.len() + TAG_LEN bytes of the provided buffer.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`libcrux-chacha20poly1305`	all versions	0.0.8`cargo update -p libcrux-chacha20poly1305 --precise 0.0.8`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for libcrux-chacha20poly1305, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update libcrux-chacha20poly1305 to 0.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hc3c-63hc-2r9f 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

An application that passes in a ciphertext buffer of length greater than `ptxt.len() + TAG_LEN` to `libcrux_chacha20poly1305::encrypt` or `libcrux_chacha20poly1305::xchacha20_poly1305::encrypt` would experience a panic. ## Impact An application where the length of the ciphertext buffer is under attacker control could be made to crash. ## Mitigation The fix makes it so that `libcrux_chacha20poly1305::encrypt` and `libcrux_chacha20poly1305::xchacha20_poly1305::encrypt` no longer panic in this case, but instead write out the ciphertext and tag into the first `ptxt.len() + TAG_LEN` bytes of the

O3 Security · Impact-Aware SCA

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