s2n-tls has a potentially observable differences in RSA premaster secret handling

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

When receiving a message from a client that sent an invalid RSA premaster secret, an issue in s2n-tls results in the server performing additional processing when the premaster secret contains an incorrect client hello version. While no practical attack on s2n-tls has been demonstrated, this causes a small timing difference which could theoretically be used as described in the Marvin Attack [1]. We would like to thank Hubert Kario [2] for reporting this issue. Impact The extent of this issue is a timing difference. No practical attack on s2n-tls has been demonstrated. This issue affects server applications that permit RSA key exchange. Applications that use the default, built-in blinding feature or properly implement self-service blinding are not affected. Impacted versions: <= v1.4.15. Patches The patch is included in v1.4.16 [3]. Workarounds Applications can work around this issue by using an s2n-tls security policy that disallows RSA key exchange. If you have any questions or…

Published by the source

6 Jun 2024, 14:26 UTC

Last modified by the source

6 Jun 2024, 14:26 UTC

Source last checked

26 Oct 2026, 15:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-52xf-5p2m-9wrv

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# Patch Next advisory brief: GHSA-52xf-5p2m-9wrv

Advisory: s2n-tls has a potentially observable differences in RSA premaster secret handling
IDs: GHSA-52xf-5p2m-9wrv
Record: https://patchnext.com/advisories/ghsa-52xf-5p2m-9wrv (revision 1, source checked 26 Oct 2026, 15:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: s2n-tls 0.2.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io s2n-tls: affected <= 0.2.6; fixed in 0.2.7

## Suggested inspection (read-only)
- crates.io s2n-tls: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on s2n-tls.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-52xf-5p2m-9wrv (GitHub-reviewed advisory GHSA-52xf-5p2m-9wrv lists affected ranges: crates.io s2n-tls >=0 <=0.2.6)

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