vodozemac's usage of non-constant time base64 decoder could lead to leakage of secret key material

Exploitation

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

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2024-40640: 0.20% estimated exploitation activity in the next 30 days; percentile 9.99 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Versions before 0.7.0 of vodozemac use a non-constant time base64 implementation for importing key material for Megolm group sessions and PkDecryption Ed25519 secret keys. This flaw might allow an attacker to infer some information about the secret key material through a side-channel attack. Impact The use of a non-constant time base64 implementation might allow an attacker to observe timing variations in the encoding and decoding operations of the secret key material. This could potentially provide insights into the underlying secret key material. The impact of this vulnerability is considered low because exploiting the attacker is required to have access to high precision timing measurements, as well as repeated access to the base64 encoding or decoding processes. Additionally, the estimated leakage amount is bounded and low according to the referenced paper. Patches The patch is in commit 734b6c6948d4b2bdee3dd8b4efa591d93a61d272. Workarounds None. References A detailed description…

Published by the source

17 Jul 2024, 18:30 UTC

Last modified by the source

18 Nov 2024, 16:26 UTC

Source last checked

26 Oct 2026, 15:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-j8cm-g7r6-hfpq

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# Patch Next advisory brief: CVE-2024-40640

Advisory: vodozemac's usage of non-constant time base64 decoder could lead to leakage of secret key material
IDs: CVE-2024-40640, GHSA-j8cm-g7r6-hfpq
Record: https://patchnext.com/advisories/cve-2024-40640 (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: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vodozemac 0.7.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io vodozemac: affected < 0.7.0; fixed in 0.7.0

## Suggested inspection (read-only)
- crates.io vodozemac: 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 vodozemac.
- 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-j8cm-g7r6-hfpq (GitHub-reviewed advisory GHSA-j8cm-g7r6-hfpq lists affected ranges: crates.io vodozemac >=0 <0.7.0)

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