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CVE-2026-59842

Libssh: libssh: information disclosure via short gssapi curve25519 public key

3.7 LowFix available

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.49%Up 0.2 points since Jul 22, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.7

Libssh: libssh: information disclosure via short gssapi curve25519 public key

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
CVE-2026-59842
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-125
Updated
2026-11-06
EUVDEUVD-2026-46176 3.7

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
EUVD-2026-46176
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-06
GitHub AdvisoriesGHSA-x94w-cg8g-g593 3.7

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519...

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
GHSA-x94w-cg8g-g593
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-125
Updated
2026-11-02
NVD 3.7

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
CVE-2026-59842
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-125
Updated
2026-11-06
OSVALPINE-CVE-2026-59842 5.3

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
ALPINE-CVE-2026-59842
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-03
OSVBELL-CVE-2026-59842 5.3
Record
BELL-CVE-2026-59842
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
Show 7 moreShow less
OSV 3.7

Libssh: libssh: information disclosure via short gssapi curve25519 public key

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
CVE-2026-59842
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-125
Updated
2026-11-07
OSVDEBIAN-CVE-2026-59842 5.3

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
DEBIAN-CVE-2026-59842
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-07
OSVRHSA-2026:42922 8.8

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Record
RHSA-2026:42922
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRHSA-2026:55855 8.8

Red Hat Security Advisory: libssh security update

Record
RHSA-2026:55855
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRLSA-2026:55855 8.8

Important: libssh security update

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

  • libssh: libssh: information disclosure via short GSSAPI Curve25519 public key (CVE-2026-59842)

  • libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843)

  • libssh: libssh: denial of service via oversized SFTP read length (CVE-2026-59844)

  • libssh: libssh: denial of service via unchecked ProxyCommand fork() failure (CVE-2026-59845)

  • libssh: libssh: information disclosure via ProxyCommand %r username expansion (CVE-2026-59846)

  • libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification (CVE-2026-59847)

  • libssh: libssh: denial of service via SFTP responses with unknown request IDs (CVE-2026-59848)

  • libssh: libssh: denial of service via automatic certificate authentication loop (CVE-2026-59849)

  • libssh: libssh: use-after-free via data callbacks on closed channels (CVE-2026-59850)

  • libssh: libssh: authentication bypass via missing GSSAPI principal check (CVE-2026-59851)

  • libssh: libssh: stack buffer overflow in SFTP server longname construction (CVE-2026-15370)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
RLSA-2026:55855
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-59842 3.7

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Record
UBUNTU-CVE-2026-59842
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVALSA-2026:55855 No score

Important: libssh security update

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

  • libssh: libssh: information disclosure via short GSSAPI Curve25519 public key (CVE-2026-59842)
  • libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843)
  • libssh: libssh: denial of service via oversized SFTP read length (CVE-2026-59844)
  • libssh: libssh: denial of service via unchecked ProxyCommand fork() failure (CVE-2026-59845)
  • libssh: libssh: information disclosure via ProxyCommand %r username expansion (CVE-2026-59846)
  • libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification (CVE-2026-59847)
  • libssh: libssh: denial of service via SFTP responses with unknown request IDs (CVE-2026-59848)
  • libssh: libssh: denial of service via automatic certificate authentication loop (CVE-2026-59849)
  • libssh: libssh: use-after-free via data callbacks on closed channels (CVE-2026-59850)
  • libssh: libssh: authentication bypass via missing GSSAPI principal check (CVE-2026-59851)
  • libssh: libssh: stack buffer overflow in SFTP server longname construction (CVE-2026-15370)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
ALSA-2026:55855
Updated
2026-11-02

Affected products

Show 3 moreShow less

Affected packages

Affected packages
PackageAffectedFixed
libssh
Alpine:v3.24
 before 0.12.1-r0
0.12.1-r0
libssh
AlmaLinux:10
From an advisory covering 11 CVEs
 before 0.12.0-3.el10_2
0.12.0-3.el10_2
libssh-config
AlmaLinux:10
From an advisory covering 11 CVEs
 before 0.12.0-3.el10_2
0.12.0-3.el10_2
libssh-devel
AlmaLinux:10
From an advisory covering 11 CVEs
 before 0.12.0-3.el10_2
0.12.0-3.el10_2
libssh
Alpaquita:stream
 0.9.6-r1 up to 0.12.1-r0
0.12.1-r0
libssh
Debian:14
 before 0.12.1-1, plus listed versions
0.11.2-10.11.3-10.12.0-10.12.0-20.12.0-3
0.12.1-1
libssh
Red Hat:hummingbird:1
From an advisory covering 10 CVEs
 before 0:0.12.1-4.hum1
0:0.12.1-4.hum1
libssh-config
Red Hat:hummingbird:1
From an advisory covering 10 CVEs
 before 0:0.12.1-4.hum1
0:0.12.1-4.hum1
libssh-devel
Red Hat:hummingbird:1
From an advisory covering 10 CVEs
 before 0:0.12.1-4.hum1
0:0.12.1-4.hum1
libssh-debuginfo
Red Hat:enterprise_linux:10.2
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2
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Affected packages
PackageAffectedFixed
libssh-debugsource
Red Hat:enterprise_linux:10.2
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2
libssh-devel
Red Hat:enterprise_linux:10.2
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2
libssh
Red Hat:enterprise_linux:10.2
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2
libssh-config
Red Hat:enterprise_linux:10.2
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2
libssh
Rocky Linux:10
From an advisory covering 11 CVEs
 before 0:0.12.0-3.el10_2
0:0.12.0-3.el10_2

History

History
RecordedChangedSources
affected, facts
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-2026-59842 is a low vulnerability (CVSS 3.7) in Libssh, published July 21, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.49%, the 42nd percentile. Fixed in libssh 0.12.1-r0.

References

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