CVE-2025-8277 | Libssh: memory exhaustion via repeated key exchange in libssh

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

Published: 2025-09-09 Last update: 2026-05-19 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-8277 is rated Low Risk (19.1/100): CVSS Low severity, with low exploitation likelihood (EPSS 0.06%). Low composite risk—no urgent action required; patch on your normal maintenance cycle and revisit priority if CVSS or EPSS increases.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-8277

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-26 0.04% 0.06% +0.02%
2 2026-05-25 0.05% 0.04% -0.01%
3 2026-02-17 — 0.05% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-8277

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.1 3.1 LOW
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.6 1.4 [email protected]

Weakness enumeration for CVE-2025-8277

GitHub Security Advisory for CVE-2025-8277

GHSA-39mw-228p-wr6v · Severity: low — A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly...

OS Trackers for CVE-2025-8277

vendor priority summary link
debian not yet assigned CVE-2025-8277 not yet assigned priority: Debian including 1 source packages (libssh), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-8277
redhat low — https://access.redhat.com/security/cve/CVE-2025-8277
suse low CVE-2025-8277 severity low: SUSE including 342 source package names (0.0.17-1.1:libssh-config-0.9.8-150600.11.6.1, 0.0.17-1.1:libssh4-0.9.8-150600.11.6.1, …), 977 product×package rows across 331 product lines (Container bci/kiwi, Container bci/spack, … (331 product lines)): Fixed 746, Known Affected 231. https://www.suse.com/security/cve/CVE-2025-8277/
ubuntu low CVE-2025-8277 low priority: Ubuntu including 1 source packages (libssh), 8 status rows across 8 suites (bionic, focal, jammy, noble, plucky, questing, upstream, xenial): released 6, ignored 1, not-affected 1. https://ubuntu.com/security/CVE-2025-8277

Affected software / configurations for CVE-2025-8277

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-8277

cvelogic Threat Intelligence