# CVE-2026-82759: Reversible IP address pseudonymisation in AshAuthentication audit log hash mode

> Attackers can recover client IP addresses from audit logs due to weak hashing with predictable salts in AshAuthentication.

- **Severity:** Low 1.8 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:N/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:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** EEF-CVE-2026-82759, GHSA-cgqj-pcpq-xhfm

## What is CVE-2026-82759?

CVE-2026-82759 is a low-severity vulnerability in team-alembic ash_authentication, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Use of a One-Way Hash with a Predictable Salt vulnerability in team-alembic AshAuthentication allows readers of the audit store to recover the client IP addresses that the audit log add-on's :hash privacy mode is meant to pseudonymise.

AshAuthentication.AddOn.AuditLog.IpPrivacy.hash_ip/1 computes a single unkeyed :crypto.hash(:sha256, salt <> ip) and truncates the result to 16 hexadecimal characters. The salt is read from the :audit_log_ip_salt or :secret application config keys, and falls back to the constant "default-salt-change-in-production" published in the library source when neither is set, with nothing warning that the default is in use. The IPv4 space is only 2^32 values and SHA-256 is fast, so the whole hash table is precomputable and every stored value maps back to its source address. Truncating to 16 characters does not help, and even a configured salt leaves the hash cheap enough to enumerate once it leaks.

This issue affects ash_authentication: from 4.12.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

Weakness: CWE-760 (Use of a One-Way Hash with a Predictable Salt)

## Which versions are affected by CVE-2026-82759?

1 open source package ship an affected version, including ash_authentication.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_authentication` | Hex | From 4.12.0 | 4.15.0, 5.0.0-rc.14 |

## How do I fix CVE-2026-82759?

Upgrade ash_authentication to a fixed version for your release line: 4.15.0 or 5.0.0-rc.14.

## Is CVE-2026-82759 being exploited?

There is no known exploitation of CVE-2026-82759 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82759 and fix it if it is affected.

What it is: CVE-2026-82759 is a low-severity vulnerability in team-alembic ash_authentication, published on 17 Sep 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-2026-82759 in the wild and no public exploit code.

Affected packages and fixed versions:
- ash_authentication (Hex): affected from 4.12.0; fixed in 4.15.0, 5.0.0-rc.14

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-2026-82759/ (Markdown: https://insights.sbomify.com/CVE-2026-82759/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82759
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82759
- OSV: https://osv.dev/vulnerability/CVE-2026-82759

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82759/
Summaries are generated and may contain mistakes; the official description above is the record.