Usage of non-constant time base64 decoder could lead to leakage of secret key material in vodozemac
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-208.
Summary
vodozemac is an open source implementation of Olm and Megolm in pure Rust. 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. 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. This has been patched in commit 734b6c6948d4b2bdee3dd8b4efa591d93a61d272 which has been included in release version 0.7.0. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| matrix-org | vodozemac | before 0.7.0 | 0.7.0 | Patch available | CNA |
| — | vodozemac (crates.io) | before 0.7.0 | 0.7.0 | Patch available | GHSA-j8cm-g7r6-hfpq |
- vodozemac Vendormatrix-org Affected before 0.7.0 Fixed in 0.7.0 Patch available CNA
- vodozemac (crates.io) Vendor— Affected before 0.7.0 Fixed in 0.7.0 Patch available GHSA-j8cm-g7r6-hfpq
Remediation
- Fix · CNA vodozemac (matrix-org) Fixed in 0.7.0
- Fix · GHSA-j8cm-g7r6-hfpq vodozemac (crates.io) Fixed in 0.7.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2024-40640
- 2026-10-03 Alias added: GHSA-j8cm-g7r6-hfpq
References
Other 6
- https://github.com/matrix-org/vodozemac/security/advisories/GHSA-j8cm-g7r6-hfpq
- https://github.com/matrix-org/vodozemac/commit/734b6c6948d4b2bdee3dd8b4efa591d93a61d272
- https://arxiv.org/abs/2108.04600
- https://github.com/matrix-org/vodozemac/commit/77765dace11266ef9523301624a01265c6e0f790
- https://github.com/matrix-org/vodozemac
- https://rustsec.org/advisories/RUSTSEC-2024-0354.html
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Sources
- CVE-2024-40640 · CVE Program
- CVE-2024-40640 · NVD
- FIRST EPSS
- GHSA-j8cm-g7r6-hfpq · GitHub Advisory Database · CC BY 4.0
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