CVE-2025-15661: libssh2 Out-of-bounds Read
Vulnerability summary
CVE-2025-15661 is a high (CVSS 8.3) Out-of-bounds Read vulnerability in libssh2. EPSS estimates a 0.65% chance of exploitation in the next 30 days, higher than 50% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 12 · Related 13Timeline
- 18-06-2026PublishedVulnerability first disclosed.
- 24-09-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
11 scores · 8 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · WolfiEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
- NVDNIST8.3HighCVSS:4.0/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
- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
- OSV · Red hatEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
EPSS trend
Probability
0.65%
Chance of exploitation in the next 30 days
Percentile
50%
Versus all other CVEs
30-day change
0.00 pp
From 0.65% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Chainguard3 products
- libssh2< 1.11.1-r7
- libssh2-dev< 1.11.1-r7
- libssh2-doc< 1.11.1-r7
Redhat3 products
- libssh2< 0:1.11.1-9.hum1
- libssh2-devel< 0:1.11.1-9.hum1
- libssh2-docs< 0:1.11.1-9.hum1
Wolfi3 products
- libssh2< 1.11.1-r7
- libssh2-dev< 1.11.1-r7
- libssh2-doc< 1.11.1-r7
Alpine1 product
- rust< 1.96.1-r0
Debian1 product
- libssh2< 1.10.0-3+deb12u1 | < 1.11.1-1+deb13u1 | < 1.11.1-4
Libssh21 product
- libssh2≤ 1.11.1
Ubuntu1 product
- libssh2All versions (No fix recorded) | < 1.11.0-4.1ubuntu0.24.04.2 | < 1.11.1-1ubuntu0.25.10.2 | < 1.11.1-1ubuntu0.26.04.2
7 vendors · 13 products
References
18 links- www.vulncheck.com/advisories/libssh2-heap-buffer-over-read-via-sftp-symlink-in-sftp-cThird Party AdvisoryARTICLEREPORTAdvisory
- images.redhat.comARTICLE
Show all 18 references
- github.com/libssh2/libssh2PACKAGE