Post-Quantum Secure Feldman's Verifiable Secret Sharing has Timing Side-Channels in Matrix Operations

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2025-29780: 0.23% estimated exploitation activity in the next 30 days; percentile 13.96 (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.

Description: The feldmanvss library contains timing side-channel vulnerabilities in its matrix operations, specifically within the findsecurepivot function and potentially other parts of securematrixsolve. These vulnerabilities are due to Python's execution model, which does not guarantee constant-time execution. An attacker with the ability to measure the execution time of these functions (e.g., through repeated calls with carefully crafted inputs) could potentially recover secret information used in the Verifiable Secret Sharing (VSS) scheme. The findsecurepivot function, used during Gaussian elimination in securematrixsolve, attempts to find a non-zero pivot element. However, the conditional statement if matrix[row][col] != 0 and rowrandom < minvalue: has execution time that depends on the value of matrix[row][col]. This timing difference can be exploited by an attacker. The constanttimecompare function in this file also does not provide a constant-time guarantee. This advisory…

Published by the source

14 Mar 2025, 19:55 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:31 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-q65w-fg65-79f4

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-q65w-fg65-79f4

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# Patch Next advisory brief: CVE-2025-29780

Advisory: Post-Quantum Secure Feldman's Verifiable Secret Sharing has Timing Side-Channels in Matrix Operations
IDs: CVE-2025-29780, GHSA-q65w-fg65-79f4
Record: https://patchnext.com/advisories/cve-2025-29780 (revision 3, source checked 26 Oct 2026, 13:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI postquantum-feldman-vss: affected <= 0.8.0b2

## Suggested inspection (read-only)
- `python -m pip show postquantum-feldman-vss`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on postquantum-feldman-vss.
- 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://osv.dev/vulnerability/GHSA-q65w-fg65-79f4 (OSV record GHSA-q65w-fg65-79f4 lists affected ranges: PyPI postquantum-feldman-vss >=0 <=0.8.0b2)
- Verified: https://github.com/advisories/GHSA-q65w-fg65-79f4 (GitHub-reviewed advisory GHSA-q65w-fg65-79f4 lists affected ranges: PyPI postquantum-feldman-vss >=0 <=0.8.0b2)

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