Out-of-bounds Read in Libssh2
CVE-2025-15661
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (49.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Libssh2 — versions 0, 2dae3024897e1898d389835151f4e9606227721d
Weakness classification (CWE)
References
- Researcher Pull Request (issue-tracking, technical-description, Patch)
- Maintainer Pull Request (issue-tracking, Patch)
- Patch Commit (Patch, patch)
- www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2025-15661?
- CVE-2025-15661 is a medium-severity vulnerability in Libssh2, classified under Out-of-bounds Read. CVSS score: 6.5/10. Published 2026-06-18.
- How severe is CVE-2025-15661?
- Medium severity. CVSS v3 base score is 6.5 out of 10.