CVE-2025-15661
libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c
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.
INFO
Published Date :
June 18, 2026, 9:16 p.m.
Last Modified :
July 14, 2026, 11:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update to a version of libssh2 with commit 2dae302 applied.
- Ensure input validation checks packet buffer size before memcpy.
- Sanitize SFTP server responses.
- Monitor for unexpected crashes or memory leaks.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-15661.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-15661 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-15661
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-15661 vulnerability anywhere in the article.
-
The Hacker News
Public PoC Released for Critical libssh2 CVE-2026-55200 Client-Side SSH Flaw
A public proof-of-concept is now out for CVE-2026-55200, a critical flaw in libssh2 that lets a malicious or compromised SSH server trigger memory corruption on a connecting client, with possible code ... Read more
The following table lists the changes that have been made to the
CVE-2025-15661 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jul. 14, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://github.com/libssh2/libssh2', 'vendor': 'libssh2', 'product': 'libssh2', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '1.11.1'}, {'status': 'unaffected', 'version': '2dae3024897e1898d389835151f4e9606227721d', 'versionType': 'git'}], 'defaultStatus': 'affected'}] [{'repo': 'https://github.com/libssh2/libssh2', 'vendor': 'libssh2', 'product': 'libssh2', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '1.11.1'}, {'status': 'unaffected', 'version': '2dae3024897e1898d389835151f4e9606227721d', 'versionType': 'git'}], 'packageURL': 'pkg:github/libssh2/libssh2', 'defaultStatus': 'affected'}] -
Initial Analysis by [email protected]
Jun. 26, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:* versions up to (including) 1.11.1 Added Reference Type VulnCheck: https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d Types: Patch Added Reference Type VulnCheck: https://github.com/libssh2/libssh2/pull/1705 Types: Patch Added Reference Type VulnCheck: https://github.com/libssh2/libssh2/pull/1717 Types: Patch Added Reference Type VulnCheck: https://www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-c Types: Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 22, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2025-15661', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-22T18:07:05.411976Z'} -
New CVE Received by [email protected]
Jun. 18, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/libssh2/libssh2', 'vendor': 'libssh2', 'product': 'libssh2', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '1.11.1'}, {'status': 'unaffected', 'version': '2dae3024897e1898d389835151f4e9606227721d', 'versionType': 'git'}], 'defaultStatus': 'affected'}] Added 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. Added CVSS V4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H Added CWE CWE-125 Added Reference https://github.com/libssh2/libssh2/commit/2dae3024897e1898d389835151f4e9606227721d Added Reference https://github.com/libssh2/libssh2/pull/1705 Added Reference https://github.com/libssh2/libssh2/pull/1717 Added Reference https://www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-c