# CVE-2026-111458: ssldump Heap Buffer Overflow in FAN/1 X.509 Fingerprint Formatting

> A heap buffer overflow in ssldump allows attackers to execute arbitrary code or cause denial of service via crafted pcap files when FAN/1 fingerprinting is enabled.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/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:** A user has to click or open something
- **Fix available:** No
- **Published:** 16 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-111458, GHSA-px2j-96c7-vxc7, UBUNTU-CVE-2026-111458

## What is CVE-2026-111458?

CVE-2026-111458 is a medium-severity memory corruption vulnerability in adulau ssldump, published on 16 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The fanx_fingerprint function in ssl/sslxprint.c of ssldump allocates a heap buffer for formatting FAN/1 X.509 certificate fingerprints. The allocation size is computed as strlen(b64) + strlen(hex) + 31, but the format string "fan1:x509:server:passive:%s:sha256:%s" contains 33 fixed characters in addition to the two variable-length fields and a null terminator, requiring strlen(b64) + strlen(hex) + 34 bytes. This miscalculation results in a 3-byte heap-based buffer overflow on every invocation of the function with valid inputs. The overflow occurs because sprintf writes the full formatted string into the undersized heap buffer without bounds checking. An attacker who can supply a crafted pcap file containing a TLS X.509 certificate to a user running ssldump with FAN/1 fingerprinting enabled (for example with the -j -N options) can trigger the overflow. The resulting heap corruption may lead to denial of service through a crash or, in a worst-case scenario, arbitrary code execution in the context of the user running ssldump. The vulnerability is deterministic and requires no special privileges beyond the ability to provide input to the tool.

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-111458?


## How do I fix CVE-2026-111458?

No fix has been published for CVE-2026-111458 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-111458 being exploited?

There is no known exploitation of CVE-2026-111458 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-111458 and fix it if it is affected.

What it is: CVE-2026-111458 is a medium-severity memory corruption vulnerability in adulau ssldump, published on 16 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-111458 in the wild and no public exploit code.

Affected product: adulau ssldump. 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-2026-111458/ (Markdown: https://insights.sbomify.com/CVE-2026-111458/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-111458
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-111458
- OSV: https://osv.dev/vulnerability/CVE-2026-111458

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-111458/
Summaries are generated and may contain mistakes; the official description above is the record.