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CVE-2025-5449

Libssh: integer overflow in libssh sftp server packet length validation leading to denial of service

6.5 MediumFix available

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

1.03%Up 1.0 points since Jul 26, 2025
90%50%10%1%

What each source reports

CVE List Score used 6.5

Libssh: integer overflow in libssh sftp server packet length validation leading to denial of service

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-190
Updated
2026-11-05
EUVDEUVD-2025-22738 6.5

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
EUVD-2025-22738
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-05
GitHub AdvisoriesGHSA-q9x7-4rf7-4xq2 4.3

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an...

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
GHSA-q9x7-4rf7-4xq2
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-190
Updated
2026-11-02
NVD 6.5

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-190
Updated
2026-11-05
OSVALPINE-CVE-2025-5449 6.5

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
ALPINE-CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-03
OSVBELL-CVE-2025-5449 6.5
Record
BELL-CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 7 moreShow less
OSV 6.5

Libssh: integer overflow in libssh sftp server packet length validation leading to denial of service

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-190
Updated
2026-11-07
OSVDEBIAN-CVE-2025-5449 6.5

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
DEBIAN-CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVJLSEC-2025-100 6.5

A flaw was found in the SFTP server message decoding logic of libssh

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
JLSEC-2025-100
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2025-5449 6.5

A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

Record
UBUNTU-CVE-2025-5449
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVMGASA-2026-0189 No score

Updated libssh packages fix security vulnerabilities

CVE-2025-4877 Write beyond bounds in binary to base64 conversion functions CVE-2025-4878 Use of uninitialized variable in privatekey_from_file() CVE-2025-5318 Likely read beyond bounds in sftp server handle management CVE-2025-5351 Double free in functions exporting keys CVE-2025-5372 ssh_kdf() returns a success code on certain failures CVE-2025-5449 Likely read beyond bounds in sftp server message decoding CVE-2025-5987 Invalid return code for chacha20 poly1305 with OpenSSL backend

Record
MGASA-2026-0189
Updated
2026-11-02
OSVopenSUSE-SU-2025:15243-1 No score

libssh-config-0.11.2-1.1 on GA media

These are all security issues fixed in the libssh-config-0.11.2-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2025:15243-1
Updated
2026-11-02
OSVUSN-7619-1 No score

libssh vulnerabilities

Ronald Crane discovered that libssh incorrectly handled certain base64 conversions. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-4877)

Ronald Crane discovered that libssh incorrectly handled the privatekey_from_file() function. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-4878)

Ronald Crane discovered that libssh incorrectly handled certain memory operations in the sftp server. An attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. (CVE-2025-5318, CVE-2025-5449)

Ronald Crane discovered that libssh incorrectly handled exporting keys. An attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. This issue only affected Ubuntu 24.04 LTS, Ubuntu 24.10, and Ubuntu 25.04. (CVE-2025-5351)

Ronald Crane discovered that libssh incorrectly handled the ssh_kdf() function. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-5372)

Ronald Crane discovered that libssh incorrectly handled the ChaCha20 cipher. An attacker could possibly use this issue to cause libssh to use partially initialized cypher content. This issue only affected Ubuntu 24.04 LTS, Ubuntu 24.10, and Ubuntu 25.04. (CVE-2025-5987)

Record
USN-7619-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libssh
Alpine:v3.22
before 0.11.2-r0
0.11.2-r0
libssh
Alpine:v3.23
before 0.11.2-r0
0.11.2-r0
libssh
Alpine:v3.24
before 0.11.2-r0
0.11.2-r0
libssh
Alpaquita:25
0.11.1-r0 up to 0.11.2-r0
0.11.2-r0
libssh
Alpaquita:stream
0.11.1-r0 up to 0.11.2-r0
0.11.2-r0
libssh
Debian:13
before 0.11.2-1
0.11.2-1
libssh
Debian:14
before 0.11.2-1
0.11.2-1
libssh_jll
Julia
0.11.0+0 up to 0.11.3+0
0.11.3+0
libssh
Mageia:9
From an advisory covering 7 CVEs
before 0.10.6-1.1.mga9
0.10.6-1.1.mga9
libssh
Ubuntu:22.04:LTS
From an advisory covering 7 CVEs
before 0.9.6-2ubuntu0.22.04.4, plus listed versions
0.9.6-10.9.6-1build10.9.6-20.9.6-2build10.9.6-2ubuntu0.22.04.10.9.6-2ubuntu0.22.04.20.9.6-2ubuntu0.22.04.3
0.9.6-2ubuntu0.22.04.4
libssh
Ubuntu:24.04:LTS
From an advisory covering 7 CVEs
before 0.10.6-2ubuntu0.1, plus listed versions
0.10.5-3ubuntu10.10.5-3ubuntu20.10.6-20.10.6-2build10.10.6-2build2
0.10.6-2ubuntu0.1
libssh
openSUSE:Tumbleweed
From an advisory covering 7 CVEs
before 0.11.2-1.1
0.11.2-1.1

History

History
RecordedChangedSources
affectedEUVD, NVD, OSV
factsCVE List
affected, aliases, referencesOSV
affected
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-5449 is a medium vulnerability (CVSS 6.5) in Libssh, published June 25, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.03%, the 63rd percentile. Fixed in libssh 0.11.2-r0.

References

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