CVE-2026-59843: libssh Infinite Loop
CVSS: 6.5v3.1MediumModified
AliasesUBUNTU-CVE-2026-59843DEBIAN-CVE-2026-59843CGA-34wp-g234-fw29CGA-6w9g-wx59-2vqxCGA-8w5c-xq5r-fw6gCGA-f365-39xq-qr8rCGA-g82x-69qm-95wgCGA-hqgx-xj9w-3498
Published 21-07-2026Last modified 01-09-2026
Vulnerability summary
CVE-2026-59843 is a medium (CVSS 6.5) Infinite Loop vulnerability in libssh. EPSS estimates a 0.73% chance of exploitation in the next 30 days, higher than 53.1% of scored vulnerabilities.
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)EPSS score
0.73%
0%100%
Low · +0.16 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 16 · Related 12MGASA-2026-0425OPENSUSE-SU-2026:11377-1OPENSUSE-SU-2026:21444-1RHSA-2026:42922RHSA-2026:55855RHSA-2026:62217RHSA-2026:62218SUSE-SU-2026:22940-1SUSE-SU-2026:22948-1SUSE-SU-2026:22956-1SUSE-SU-2026:23056-1SUSE-SU-2026:23168-1SUSE-SU-2026:3302-1SUSE-SU-2026:3330-1SUSE-SU-2026:3463-1USN-8699-1CGA-W8M5-5C9R-4R59
Timeline
- 21-07-2026PublishedVulnerability first disclosed.
- 01-09-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 versionMedium 6.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.73%
Chance of exploitation in the next 30 days
Percentile
53%
Versus all other CVEs
30-day change
+0.16 pp
From 0.57% on 18-09-2026
18-09-202618-10-2026
EPSS score0.73%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.
- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
Affected systems
Chainguard3 products
- libssh< 0.12.2-r0
- libssh-dev< 0.12.2-r0
- libssh2All versions (No fix recorded)
Wolfi3 products
- libssh< 0.12.2-r0
- libssh-dev< 0.12.2-r0
- libssh2All versions (No fix recorded)
Redhat2 products
- enterprise_linux8.0 | 9.0 | 10.0
- hardened_imagesna
Debian1 product
- libsshAll versions (No fix recorded) | < 0.11.5-0+deb13u1 | < 0.12.2-1
Libssh1 product
- libsshna
Ubuntu1 product
- libsshAll versions (No fix recorded) | < 0.9.6-2ubuntu0.22.04.8 | < 0.10.6-2ubuntu0.5 | < 0.11.3-1ubuntu2.1
6 vendors · 11 products
