RHSA-2026:29950
Vulnerability from csaf_redhat - Published: 2026-06-25 13:02 - Updated: 2026-06-26 19:24Summary
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Severity
Important
Notes
Topic: An update for Red Hat Hardened Images RPMs is now available.
Details: This update includes the following RPMs:
libssh2:
* libssh2-1.11.1-8.hum1 (aarch64, x86_64)
* libssh2-devel-1.11.1-8.hum1 (aarch64, x86_64)
* libssh2-docs-1.11.1-8.hum1 (noarch)
* libssh2-1.11.1-8.hum1.src (src)
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
A vulnerability in libssh2 allows a malicious SSH server to freeze connected clients during the handshake process. By sending a malformed packet, the server triggers a loop that exhausts the client's CPU, resulting in a denial of service.
5.9 (Medium)
Affected products
Fixed
4 products
| Product | Identifier | Version | Remediation |
|---|---|---|---|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@aarch64 | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@noarch | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@src | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@x86_64 | — |
Vendor Fix
fix
Workaround
|
Threats
Impact
Moderate
An out-of-bounds write vulnerability exists in the libssh2 client. A remote attacker can exploit this by sending a specially crafted SSH packet with an abnormally large length value. This corrupts the application's memory and can potentially allow the attacker to execute arbitrary code on the affected system.
8.1 (High)
Affected products
Fixed
4 products
| Product | Identifier | Version | Remediation |
|---|---|---|---|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@aarch64 | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@noarch | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@src | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:libssh2-main@x86_64 | — |
Vendor Fix
fix
Workaround
|
Threats
Impact
Important
References
20 references
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"vulnerabilities": [
{
"cve": "CVE-2026-55199",
"cwe": {
"id": "CWE-606",
"name": "Unchecked Input for Loop Condition"
},
"discovery_date": "2026-06-17T20:01:26.309958+00:00",
"ids": [
{
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"text": "2490128"
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],
"notes": [
{
"category": "description",
"text": "A vulnerability in libssh2 allows a malicious SSH server to freeze connected clients during the handshake process. By sending a malformed packet, the server triggers a loop that exhausts the client\u0027s CPU, resulting in a denial of service.",
"title": "Vulnerability description"
},
{
"category": "summary",
"text": "libssh2: libssh2: Denial of Service via crafted SSH_MSG_EXT_INFO message",
"title": "Vulnerability summary"
},
{
"category": "other",
"text": "A Moderate-rated denial of service vulnerability in the libssh2 client allows a malicious SSH server to freeze the connecting application. By triggering an infinite CPU loop during the initial connection handshake, the server can render the client unresponsive. Note: Red Hat Enterprise Linux (RHEL) 8 and newer are not affected by this flaw, as they do not ship the libssh2 package.",
"title": "Statement"
},
{
"category": "general",
"text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
"title": "CVSS score applicability"
}
],
"product_status": {
"fixed": [
"Red Hat Hardened Images:libssh2-main@aarch64",
"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
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"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2490128"
},
{
"category": "external",
"summary": "https://www.cve.org/CVERecord?id=CVE-2026-55199",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-55199"
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{
"category": "external",
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"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55199"
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{
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"summary": "https://github.com/libssh2/libssh2/commit/17626857d20b3c9a1addfa45979dadcee1cd84a4",
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"url": "https://github.com/libssh2/libssh2/pull/1864"
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{
"category": "external",
"summary": "https://www.vulncheck.com/advisories/libssh2-pre-authentication-dos-via-ssh-msg-ext-info-handler",
"url": "https://www.vulncheck.com/advisories/libssh2-pre-authentication-dos-via-ssh-msg-ext-info-handler"
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"date": "2026-06-25T13:02:46+00:00",
"details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\nhttps://images.redhat.com/",
"product_ids": [
"Red Hat Hardened Images:libssh2-main@aarch64",
"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
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"details": "To mitigate this issue, ensure your libssh2 clients only connect to trusted SSH servers. You can enforce this by implementing outbound network access controls (egress filtering) to block applications from initiating connections to unknown or untrusted external hosts.",
"product_ids": [
"Red Hat Hardened Images:libssh2-main@aarch64",
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"scores": [
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"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"products": [
"Red Hat Hardened Images:libssh2-main@aarch64",
"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
]
}
],
"threats": [
{
"category": "impact",
"details": "Moderate"
}
],
"title": "libssh2: libssh2: Denial of Service via crafted SSH_MSG_EXT_INFO message"
},
{
"cve": "CVE-2026-55200",
"discovery_date": "2026-06-17T20:01:16.724927+00:00",
"ids": [
{
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"text": "2490127"
}
],
"notes": [
{
"category": "description",
"text": "An out-of-bounds write vulnerability exists in the libssh2 client. A remote attacker can exploit this by sending a specially crafted SSH packet with an abnormally large length value. This corrupts the application\u0027s memory and can potentially allow the attacker to execute arbitrary code on the affected system.",
"title": "Vulnerability description"
},
{
"category": "summary",
"text": "libssh2: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c",
"title": "Vulnerability summary"
},
{
"category": "other",
"text": "An Important out-of-bounds write vulnerability was discovered in libssh2. As it only impacts client installations of the library, exploitation would require a victim to initiate an SSH connection to an attacker-controlled server. This means an attacker must first redirect client connections via DNS poisoning, a man-in-the-middle, or compromise of a trusted host. While the vulnerability does not require authentication and requires no special configuration, the client redirection prerequisites significantly limit the practical attack surface compared to a server-side flaw.\n\nThe integer overflow provides uncontrolled access to the heap, which reliably crashes the client process but is unlikely to achieve remote code execution in practice. Weaponizing the overflow for code execution would require a separate information disclosure vulnerability to defeat ASLR, along with a specific heap layout to place exploitable structures adjacent to the undersized allocation. On RHEL, ASLR is enabled by default and glibc\u0027s heap metadata integrity checks further raise the bar, making denial of service the realistic impact for most deployments.\n\nRed Hat Enterprise Linux (RHEL) 8 and newer are not affected by this flaw, as they do not ship the libssh2 package.",
"title": "Statement"
},
{
"category": "general",
"text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
"title": "CVSS score applicability"
}
],
"product_status": {
"fixed": [
"Red Hat Hardened Images:libssh2-main@aarch64",
"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
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"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2490127"
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"summary": "https://www.cve.org/CVERecord?id=CVE-2026-55200",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-55200"
},
{
"category": "external",
"summary": "https://nvd.nist.gov/vuln/detail/CVE-2026-55200",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55200"
},
{
"category": "external",
"summary": "https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8",
"url": "https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"
},
{
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"summary": "https://github.com/libssh2/libssh2/pull/2052",
"url": "https://github.com/libssh2/libssh2/pull/2052"
},
{
"category": "external",
"summary": "https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c",
"url": "https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"
}
],
"release_date": "2026-06-17T19:03:15.183000+00:00",
"remediations": [
{
"category": "vendor_fix",
"date": "2026-06-25T13:02:46+00:00",
"details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\nhttps://images.redhat.com/",
"product_ids": [
"Red Hat Hardened Images:libssh2-main@aarch64",
"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
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"restart_required": {
"category": "none"
},
"url": "https://access.redhat.com/errata/RHSA-2026:29950"
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{
"category": "workaround",
"details": "The primary mitigation is strict network access control. Ensure libssh2 clients only connect to trusted SSH servers, and use firewalls to block untrusted incoming connections if libssh2 is deployed as a server-side application.",
"product_ids": [
"Red Hat Hardened Images:libssh2-main@aarch64",
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"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
]
}
],
"scores": [
{
"cvss_v3": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 8.1,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
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"Red Hat Hardened Images:libssh2-main@noarch",
"Red Hat Hardened Images:libssh2-main@src",
"Red Hat Hardened Images:libssh2-main@x86_64"
]
}
],
"threats": [
{
"category": "impact",
"details": "Important"
}
],
"title": "libssh2: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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