CVE-2025-15661 libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c
A malicious SSH server can trigger a heap buffer over-read in libssh2, potentially disclosing memory contents or causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-15661?
CVE-2025-15661 is a high-severity vulnerability in libssh2, published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-125
Which versions are affected by CVE-2025-15661?
It affects 1 product.
Linux distribution packages (3)
libssh2 Red Hat:hummingbird:1 | All versions | 0:1.11.1-9.hum1 |
libssh2-devel Red Hat:hummingbird:1 | All versions | 0:1.11.1-9.hum1 |
libssh2-docs Red Hat:hummingbird:1 | All versions | 0:1.11.1-9.hum1 |
Products include Libssh2 Libssh2.
How do I fix CVE-2025-15661?
Apply the vendor's patch.
Is CVE-2025-15661 being exploited?
There is no known exploitation of CVE-2025-15661 in the wild and no public exploit code.
Other vulnerabilities in libssh2
- CVE-2026-55200 libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
- CVE-2026-66032 libssh2 Double-Free Heap Corruption via sftp_open()
- CVE-2026-66033 libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation
- CVE-2026-58050 libssh2 - Integer Overflow in publickey Subsystem Attribute Allocation
- CVE-2026-58051 libssh2 - Free of Uninitialized Pointer in publickey List Cleanup
Sources
Also known as ALPINE-CVE-2025-15661, AZL-90936, BELL-CVE-2025-15661, DEBIAN-CVE-2025-15661, ECHO-16dd-65e4-250c, GHSA-3wqh-87fg-ffgg and 5 more.