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No exploitation reportedFix available

CVE-2026-59843

No exploitation reported by the sources we read.

  • Published2026-07-21
  • WeaknessCWE-400 · CWE-835

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A flaw was found in libssh. A remote authenticated peer can advertise a zero maximum packet size in SSH_MSG_CHANNEL_OPEN, causing later channel writes to loop indefinitely and consume CPU, leading to denial of service.

Timeline

dates in UTC
  1. 2026-07-2112:18CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-59843?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-59843?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Libssh
BranchAffectedFixed in
—all versionsno fix published
Redhat enterprise linux
BranchAffectedFixed in
8.0= 8.0no fix published
9.0= 9.0no fix published
10.0= 10.0no fix published
Redhat hardened images
BranchAffectedFixed in
—all versionsno fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA4 products

As redhat, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-09-01

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • libsshWolfiall versions · fixed in 0.12.2-r0and 1 other package
  • libsshUbuntu:Pro:20.04:LTSall versions · no fixed version listed
  • libsshUbuntu:Pro:18.04:LTSall versions · no fixed version listed
  • libsshUbuntu:Pro:16.04:LTSall versions · no fixed version listed
  • libsshUbuntu:26.04:LTSall versions · fixed in 0.11.3-1ubuntu2.1
  • libsshUbuntu:24.04:LTSall versions · fixed in 0.10.6-2ubuntu0.5
  • libsshUbuntu:22.04:LTSall versions · fixed in 0.9.6-2ubuntu0.22.04.8
  • libsshTuxCare:AlmaLinux:9.6all versions · fixed in 0.10.4-15.el9_6.tuxcare.els10and 2 other packages

56 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-59843 Red Hat Product Security94 products fixed

    libssh: libssh: denial of service via zero advertised channel packet size

  • RHSA-2026:62218 Red Hat Product Security32 products fixed

    Red Hat Security Advisory: libssh security update

  • RHSA-2026:62217 Red Hat Product Security32 products fixed

    Red Hat Security Advisory: libssh security update

  • RHSA-2026:55855 Red Hat Product Security26 products fixed

    Red Hat Security Advisory: libssh security update

  • RHSA-2026:42922 Red Hat Product Security7 products fixed

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

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2026:62218 · 32 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  2. Vendor fix Red Hat Product Security RHSA-2026:42922 · 7 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
  3. Workaround from the vendor Red Hat Product Security RHSA-2026:62218 · 32 productsNo workaround available.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Published
2026-07-21
Last Modified
2026-09-01
NVD status
Modified
GitHub Advisory
GHSA-4846-7xwg-pw5m

Frequently asked questions

What is CVE-2026-59843?

A flaw was found in libssh. A remote authenticated peer can advertise a zero maximum packet size in SSH_MSG_CHANNEL_OPEN, causing later channel writes to loop indefinitely and consume CPU, leading to denial of service.

Is CVE-2026-59843 actively exploited?

Active exploitation of CVE-2026-59843 has not been confirmed. Its EPSS score was 0.6% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-59843?

CVE-2026-59843 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

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Sources for this record