# CVE-2026-55787: Flyto2 Core: SSRF guard bypass via IPv6 transition addresses (IPv4-mapped / 6to4 / NAT64) in validate_url_ssrf > Authenticated users can bypass SSRF protections using IPv6 transition addresses to access internal services and cloud metadata. - **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 14 Oct 2026 - **Updated:** 15 Oct 2026 - **Also known as:** GHSA-794r-5rp2-fpg8, PYSEC-2026-2481 ## What is CVE-2026-55787? CVE-2026-55787 is a high-severity server-side request forgery vulnerability in flytohub flyto-core, published on 14 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description Flyto2 Core is an execution kernel for automation and AI-agent workflows. Prior to 2.26.3, validate_url_ssrf and is_private_ip in src/core/utils.py compare resolved addresses only against native private IPv4 and IPv6 ranges and do not unwrap IPv4-mapped, IPv4-compatible, 6to4, or NAT64 transition addresses. An authenticated workflow author can provide a transition-form literal URL through the Execution API POST /v1/execute route, http.get, or sibling guarded outbound-request modules, causing the guard to accept an address whose embedded IPv4 points to loopback, RFC 1918, or cloud metadata services. On a host that routes the selected transition form, the outbound request reaches the internal destination and returns the response body to the workflow caller, enabling read SSRF and disclosure of internal-service data or cloud credentials. This issue is fixed in version 2.26.3. Weakness: CWE-918 (Server-Side Request Forgery) ## Which versions are affected by CVE-2026-55787? 3 open source packages ship an affected version, including flyto-core. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `flyto-core` | PyPI | All versions | 2.26.3 | | `flyto-core` | PyPI | All versions | 2.26.3 | | `flyto-core` | PyPI | All versions | 2.26.3 | ## How do I fix CVE-2026-55787? Upgrade flyto-core to 2.26.3 or later. ## Is CVE-2026-55787 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55787 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-55787 and fix it if it is affected. What it is: CVE-2026-55787 is a high-severity server-side request forgery vulnerability in flytohub flyto-core, published on 14 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55787 exists. Affected packages and fixed versions: - flyto-core (PyPI): affected all versions; fixed in 2.26.3 - flyto-core (PyPI): affected all versions; fixed in 2.26.3 - flyto-core (PyPI): affected all versions; fixed in 2.26.3 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-2026-55787/ (Markdown: https://insights.sbomify.com/CVE-2026-55787/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55787 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55787 - OSV: https://osv.dev/vulnerability/CVE-2026-55787 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-55787/ Summaries are generated and may contain mistakes; the official description above is the record.