How severe is CVE-2025-15661?

CVE-2025-15661 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability high.

Is CVE-2025-15661 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-15661?

CVE-2025-15661 affects Libssh2. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-15661?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-15661 have an EU (EUVD) identifier?

Yes. CVE-2025-15661 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-210285.

When was CVE-2025-15661 published?

CVE-2025-15661 was published on 2026-06-18 and last updated on 2026-06-26.

CVE-2025-15661

CVE-2025-15661 is a medium-severity vulnerability in Libssh2 with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 8.3
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-210285
Weakness: CWE-125
Affected product: Libssh2
Published: 2026-06-18
Last modified: 2026-06-26

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-15661?: CVE-2025-15661 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability high.
Is CVE-2025-15661 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-15661?: CVE-2025-15661 affects Libssh2. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-15661?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-15661 have an EU (EUVD) identifier?: Yes. CVE-2025-15661 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-210285.
When was CVE-2025-15661 published?: CVE-2025-15661 was published on 2026-06-18 and last updated on 2026-06-26.

References

Affected products (1)

cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*

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