# CVE-2025-15661: libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c

Status: published. Published: 2026-06-18. Updated: 2026-11-08.

libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the missing validation of available packet buffer size before the memcpy operation.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/libssh2/libssh2/pull/1705
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/libssh2/libssh2/pull/1717
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d

## Affected products and versions

- libssh2 / libssh2 (libssh2/libssh2): ≥ 0; ≤ 1.11.1 (affected, semver); 2dae3024897e1898d389835151f4e9606227721d (unaffected, git). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.3 (high); CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.65% as of 2026-11-08; percentile 51.33%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/libssh2/libssh2/pull/1705 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/libssh2/libssh2/pull/1717 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-c (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2025-15661; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2025-15661; retrieved 2026-11-08; source updated Not reported

Revision: b6cfc5d8656ce9632ad4afa8dcfc7b43ec12670b7ba69dbffacc5ca3400a5744

Canonical: https://y2.dev/cve/CVE-2025-15661

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