CVE Intelligence
High

CVE-2025-5987 — Libssh: invalid return code for chacha20 poly1305 with openssl backend

A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.

Published Jul 7, 2025 · Updated Oct 16, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: redhat

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 1.7% (30-day exploitation probability)+12
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
1.73%
ahead of 77% of scored CVEs · Oct 16, 2026
Affects
Libssh
Libssh and 15 more
CVSS base
8.1
High · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Libssh Libssh, Red Hat Red Hat Enterprise Linux 10, Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Libssh Libssh ≥ 0.10.0 and < 0.11.2 Vulnerable NIST National Vulnerability Database
Red Hat Red Hat Enterprise Linux 10 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 9 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.13 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.14 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.15 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.16 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.17 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.18 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.19 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Red Hat Red Hat OpenShift Container Platform 4.20 versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.1 CVSS 3.1 High 2.2 5.9 secalert@redhat.com via NIST National Vulnerability Database
8.1 CVSS 3.1 High 2.2 5.9 nvd@nist.gov via NIST National Vulnerability Database
8.1 CVSS 3.1 High — — redhat via CVE Program (cve.org) e CISA ADP
5.0 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: secalert@redhat.com)
Sources disagree significantly and the divergence is under review. Every score is kept with its origin. For prioritization we use 8.1 (secalert@redhat.com via NIST National Vulnerability Database) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-393

Other CVEs with this weakness →

EPSS over time FIRST

Oct 15, 2026 → Oct 16, 2026 · 2 reading(s) · max 1.73%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · red hat/red hat enterprise linux 10, red hat/red hat enterprise linux 10.0 extended update support, red hat/red hat ente
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 16, 2026
  • Affected products added · libssh/libssh
    Oct 16, 2026 · NIST National Vulnerability Database
  • CVSS changed · 8.1
    Oct 16, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 16, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 16, 2026 · Alertas do Telegram
  • 2025
  • CVE published
    Jul 7, 2025 · redhat

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 16, 2026 – Oct 16, 2026
  • 1× Official description updated · Oct 16, 2026 – Oct 16, 2026

References

19 on the record

Elsewhere on this site

Libssh
every CVE for this vendor
CWE-393
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-89096 Nfs-utils: nfs-utils: denial of service via memory leak in rpc.statd 9h
  • CVE-2026-89085 Parted: parted: heap-based buffer overflow via crafted fat32 filesystem image 9h
  • CVE-2026-89088 Parted: parted: denial of service via heap buffer overflow during fat16 resize 9h
  • CVE-2026-111802 Nautilus: nautilus: arbitrary file deletion via trash symlink 9h
  • CVE-2026-17591 Libarchive: libarchive: use-after-free via aliased mac metadata copy 9h
  • CVE-2026-62438 Gimp: gimp: paa integer overflow out-of-bounds read 10h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-5987 is "Libssh: invalid return code for chacha20 poly1305 with openssl backend", rated High. It affects Libssh (Libssh); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 1.73% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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