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

> A compromised local attacker can bypass secure boot in Caliptra Core ROM by exploiting a TOCTOU race condition to modify firmware during loading.

- **Severity:** Medium 5.6 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Aug 2026
- **Updated:** 4 Aug 2026
- **Also known as:** GHSA-49mm-5gq5-v97f

## What is CVE-2026-11835?

CVE-2026-11835 is a medium-severity vulnerability in Caliptra Core ROM, published on 4 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-11835?


## How do I fix CVE-2026-11835?

No fix has been published for CVE-2026-11835 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11835 being exploited?

There is no known exploitation of CVE-2026-11835 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11835 and fix it if it is affected.

What it is: CVE-2026-11835 is a medium-severity vulnerability in Caliptra Core ROM, published on 4 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11835 in the wild and no public exploit code.

Affected product: Caliptra Core ROM. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-11835/ (Markdown: https://insights.sbomify.com/CVE-2026-11835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11835
- OSV: https://osv.dev/vulnerability/CVE-2026-11835

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11835/
Summaries are generated and may contain mistakes; the official description above is the record.