# CVE-2026-96596: erl_tar:extract/2 loops forever on a GNU sparse member with a trailing hole

> Attackers can cause a denial of service by supplying a crafted tar archive that triggers an infinite loop during extraction in Erlang OTP and related tools.

- **Severity:** Medium 5.9 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Oct 2026
- **Updated:** 22 Oct 2026
- **Also known as:** AZL-108207, DEBIAN-CVE-2026-96596, EEF-CVE-2026-96596, GHSA-phm5-m6cj-5382, UBUNTU-CVE-2026-96596

## What is CVE-2026-96596?

CVE-2026-96596 is a medium-severity denial of service vulnerability in Erlang OTP, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in Erlang OTP stdlib (erl_tar module), hexpm hex_core (hex_erl_tar module), hexpm hex (mix_hex_erl_tar module) and erlang rebar3 (r3_hex_erl_tar module) allows an attacker who supplies a tar archive to cause a denial of service via a crafted GNU sparse member.

When erl_tar:extract/1,2 writes a member to disk, erl_tar:stream_to_file_loop/3 reads it in chunks of 65536 bytes by default. For a GNU sparse member whose sparse map ends before its real size, erl_tar:do_sparse_read/3 matches its trailing-hole clause before its zero-length clause. After the chunk is used up, the trailing-hole clause reads zero bytes, does not advance the position, and recurses forever. A 2048-byte archive keeps the extracting process and one scheduler busy until the process is killed. The {max_size, N} option prevents this only when N is below the real size of the member. Extraction with the memory option is not affected.

hex_core ships its own copy of erl_tar as hex_erl_tar, and Hex and rebar3 ship hex_core with prefixed module names (mix_hex_erl_tar and r3_hex_erl_tar). These copies contain the same code and do not call stdlib's erl_tar, so they are affected on any OTP version. OTP 28 is not affected, but an application running on OTP 28 is affected if it extracts archives through an affected version of hex_core, Hex or rebar3.

This issue affects OTP from OTP 29.0 before OTP 29.1.2, corresponding to rebar3 from 3.27.1 before 3.28.0, and stdlib from 8.0 before 8.1.1, and hex from 2.4.2 before 2.5.3; hex_core: from 0.14.0 before 0.20.1.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-96596?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hex_core` | Hex | From 0.14.0 | 0.20.1 |

## How do I fix CVE-2026-96596?

Upgrade hex_core to 0.20.1 or later.

## Is CVE-2026-96596 being exploited?

There is no known exploitation of CVE-2026-96596 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-96596 and fix it if it is affected.

What it is: CVE-2026-96596 is a medium-severity denial of service vulnerability in Erlang OTP, published on 14 Oct 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-2026-96596 in the wild and no public exploit code.

Affected packages and fixed versions:
- hex_core (Hex): affected from 0.14.0; fixed in 0.20.1

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-2026-96596/ (Markdown: https://insights.sbomify.com/CVE-2026-96596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-96596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-96596
- OSV: https://osv.dev/vulnerability/CVE-2026-96596

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-96596/
Summaries are generated and may contain mistakes; the official description above is the record.