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CVE-2023-48795: The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products,...

The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message), and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh before 5.1.1 in Erlang/OTP, PuTTY before 0.80, AsyncSSH before 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0.10.6, libssh2 through 1.11.0, Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15, SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3, Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh crate before 0.40.2 for Rust.

MediumCVSS 5.9Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2023-48795, known as Terrapin, lets a network-positioned attacker interfere with SSH connection setup and silently remove some negotiation messages. The result can be a downgraded SSH session with certain protections disabled. It is broad across SSH clients, servers, and libraries, but the cited data does not show active exploitation.

Executive priority

Handle this as a broad dependency remediation issue, not a single server patch. Prioritize exposed SSH/SFTP services and widely deployed clients, then work through embedded libraries and appliances during normal vulnerability management cycles.

Technical view

The flaw is in SSH transport handling with certain OpenSSH extensions. Sequence number and handshake handling can allow omitted extension negotiation packets, affecting chacha20-poly1305@openssh.com and CBC Encrypt-then-MAC modes. OpenSSH before 9.6 and many SSH implementations or libraries are listed as affected.

Likely exposure

Exposure is likely wherever affected SSH, SFTP, or embedded SSH libraries are used in servers, clients, automation, appliances, developer tools, or file-transfer products. The bundle lists many affected implementations, so indirect exposure through dependencies is important.

Exploitation context

The CVSS vector is network-reachable, unauthenticated, no user interaction, but high attack complexity. The provided sources do not indicate CISA KEV listing or confirmed active exploitation, so treat exploitation as plausible but not source-confirmed.

Researcher notes

Evidence supports a protocol negotiation integrity bypass with broad implementation impact. The bundle provides affected version ranges and several vendor references, but not a complete asset-specific fix matrix or proof of active exploitation.

Mitigation direction

  • Upgrade OpenSSH to 9.6 or later where applicable.
  • Update affected SSH clients, servers, and libraries to vendor-fixed versions.
  • Prioritize internet-facing SSH and SFTP services first.
  • Review vendor guidance before changing algorithms or compatibility settings.
  • Update bundled dependencies in applications and appliances.

Validation and detection

  • Inventory SSH implementations and library versions across servers and endpoints.
  • Check SFTP gateways, appliances, and developer tools for affected SSH components.
  • Confirm OpenSSH, PuTTY, Dropbear, Paramiko, Go crypto, and AsyncSSH versions where used.
  • Verify vendor advisories or release notes show Terrapin fixes applied.
  • Document remaining legacy systems requiring compensating controls.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-354: Exact CWE lookup

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cve · low confidence lookup

CVE-2023-48795 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.9 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
3ADP providers
48Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.9CVSS 3.1MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N2.23.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.9Medium
CVSS 3.1 vector shape for CVE-2023-48795Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-354

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-354 · source CWE mapping

Improper Validation of Integrity Check Value

Improper Validation of Integrity Check Value represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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