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CVE-2026-23943· NVD / CVE Program· CNA EEF

Pre-auth SSH DoS via unbounded zlib inflate

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.66% (FIRST EPSS); higher than 50.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Erlang OTP 0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4, 26.2.5.18, 27.3.4.9; azl3 erlang 26.2.5.17-1 on Azure Linux 3.0 26.2.5.18-1; cbl2 erlang 25.3.2.21-4 on CBL Mariner 2.0 25.3.2.21-5.

Low priority for now. Upgrade to Erlang OTP 0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4, 26.2.5.18, 27.3.4.9; azl3 erlang 26.2.5.17-1 on Azure Linux 3.0 26.2.5.18-1; cbl2 erlang 25.3.2.21-4 on CBL Mariner 2.0 25.3.2.21-5 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion. The SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS. Two compression algorithms are affected: * zlib: Activates immediately after key exchange, enabling unauthenticated attacks * zlib@openssh.com: Activates post-authentication, enabling authenticated attacks Each SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments. This vulnerability is associated with program files lib/ssh/src/ssh_transport.erl and program routines ssh_transport:decompress/2, ssh_transport:handle_packet_part/4. This issue affects OTP from OTP 17.0 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to ssh from 3.0.1 before 5.5.1, 5.2.11.6 and 5.1.4.14.

MediumCVSS 6.9 · v4.0—No exploit Fix available
Published
Mar 13, 2026
Updated
Jul 24, 2026
EPSS
0.6% · 50th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
6.9
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-23943

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
erlangerlang\/otp
erlangerlang\/ssh

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • erlang erlang/otp17.0 and later · before 26.2.5.18
  • erlang erlang/otp27.0 and later · before 27.3.4.9
  • erlang erlang/otp28.0 and later · before 28.4.1
  • erlang erlang/ssh3.0.1 and later · before 5.1.4.14
  • erlang erlang/ssh5.2 and later · before 5.2.11.6
  • erlang erlang/ssh5.5 and later · up to 5.5.1 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • Erlang OTP

    • 3.0.1 and lateraffected · otpfixed in 5.5.1, 5.2.11.6, 5.1.4.14
    • 17.0 and lateraffected · otpfixed in 28.4.1, 27.3.4.9, 26.2.5.18
    • 07b8f441ca711f9812fad9e9115bab3c3aa92f79 and lateraffected · gitfixed in 43a87b949bdff12d629a8c34146711d9da93b1b1, 93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3, 0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12erlangbefore 1:25.2.3+dfsg-1+deb12u41:25.2.3+dfsg-1+deb12u4
Debian:13erlangbefore 1:27.3.4.1+dfsg-1+deb13u21:27.3.4.1+dfsg-1+deb13u2
Debian:14erlangbefore 1:27.3.4.9+dfsg-11:27.3.4.9+dfsg-1
openSUSE:Leap 16.0erlangbefore 27.1.3-160000.4.127.1.3-160000.4.1
openSUSE:Tumbleweederlang27before 27.1.3-2.127.1.3-2.1

Same product

erlang: all records

Other highest-scoring records for the same primary product.

  • CVE-2025-32433Erlang/OTP SSH Vulnerable to Pre-Authentication RCEKEV
    100Now
  • CVE-2017-1000385The Erlang otp TLS server answers with different TLS alerts to different error types in the RSA PKCS #1 1.5 padding.
    60This week
  • CVE-2022-37026In Erlang/OTP before 23.3.4.15, 24.x before 24.3.4.2, and 25.x before 25.0.2, there is a Client Authentication Bypass in certain client-cert
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-29221Apr 9, 2021 · A local privilege escalation vulnerability was discovered in Erlang/OTP prior to version 23.2.3.
    28Monitor
  • ← EarlierCVE-2026-23942Mar 13, 2026 · SFTP root escape via component-agnostic prefix check in ssh_sftpd
    21Monitor
  • Later →CVE-2026-28810Apr 7, 2026 · Predictable DNS Transaction IDs Enable Cache Poisoning in Built-in Resolver
    25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Erlang OTP0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4Vendor (CNA)
Erlang OTP26.2.5.18Vendor (CNA)
Erlang OTP27.3.4.9Vendor (CNA)
Erlang OTP28.4.1Vendor (CNA)
Erlang OTP43a87b949bdff12d629a8c34146711d9da93b1b1Vendor (CNA)
Erlang OTP5.1.4.14Vendor (CNA)
Erlang OTP5.2.11.6Vendor (CNA)
Erlang OTP5.5.1Vendor (CNA)
Erlang OTP93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3Vendor (CNA)
azl3 erlang 26.2.5.17-1 on Azure Linux 3.026.2.5.18-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 erlang 25.3.2.21-4 on CBL Mariner 2.025.3.2.21-5 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:erlang1:25.2.3+dfsg-1+deb12u4 · Debian:12Package registry (OSV)
opensuse:erlang27.1.3-160000.4.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:erlang2727.1.3-2.1 · openSUSE:TumbleweedPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-409 · Improper Handling of Highly Compressed Data (Data Amplification)

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records