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CVE-2026-55953· NVD / CVE Program· CNA EEF

TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication

The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and ssl:connect returns {ok, Socket}. All subsequent application traffic is readable and modifiable by the attacker. This issue affects OTP from OTP 17.0 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to ssl from 5.3.4 before 11.2.12.11, from 11.3 before 11.6.0.4, and from 11.7 before 11.7.4. Whether OTP before OTP 17.0, corresponding to ssl before 5.3.4, is affected is unknown.

CriticalCVSS 9.1 · v4.0—No exploit Fix available
Published
Jul 27, 2026
Updated
Sep 8, 2026
EPSS
0.4% · 29th percentile
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Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
36 / 40 · 9.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
9.1
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/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.

Affected systems

VendorProduct
erlangerlang\/otp
erlangerlang\/ssl

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 27.3.4.15
  • erlang erlang/otp28.0 and later · before 28.5.0.4
  • erlang erlang/otp29.0 and later · before 29.0.4
  • erlang erlang/ssl5.3.4 and later · before 11.2.12.11
  • erlang erlang/ssl11.3 and later · before 11.6.0.4
  • erlang erlang/ssl11.7 and later · before 11.7.4

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

    • before 17.0unknown · otp
    • 17.0 and later · before 27.3.4.15affected · otp
    • 28.0 and later · before 28.5.0.4affected · otp
    • 29.0 and later · before 29.0.4affected · otp
    • before 5.3.4unknown · otp
    • 5.3.4 and later · before 11.2.12.11affected · otp
    • 11.3 and later · before 11.6.0.4affected · otp
    • 11.7 and later · before 11.7.4affected · otp
    • 84adefa331c4159d432d22840663c38f155cd4c1 and lateraffected · gitfixed in 064e236414614f9085cbbbd6eacf0e43c02d1b4b, 0a82596d425abe43dc2e0b3d74aa1557ef74051c, e6ff938116b2872bccc478af7fefb56627285b77

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12erlangall versions—
Debian:13erlangbefore 1:27.3.4.1+dfsg-1+deb13u31:27.3.4.1+dfsg-1+deb13u3
Debian:14erlangbefore 1:29.0.4+dfsg-11:29.0.4+dfsg-1
openSUSE:Tumbleweederlang27before 27.1.3-3.127.1.3-3.1
Red Hat:hummingbird:1erlang27before 0:27.3.4.15-0.1.hum10:27.3.4.15-0.1.hum1
SUSE:Linux Enterprise Module for Server Applications 15 SP7erlangbefore 23.3.4.19-150300.3.39.123.3.4.19-150300.3.39.1
SUSE:Linux Enterprise Module for Server Applications 15 SP7erlang26before 26.2.1-150300.7.28.126.2.1-150300.7.28.1

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-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
  • CVE-2016-10253An issue was discovered in Erlang/OTP 18.x.
    39Monitor
  • CVE-2026-49759Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash
    35Monitor
  • CVE-2026-59251Denial of service via exponential certificate policy tree growth in path validation
    34Monitor
  • CVE-2026-58227TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain
    34Monitor

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 OTP064e236414614f9085cbbbd6eacf0e43c02d1b4bVendor (CNA)
Erlang OTP0a82596d425abe43dc2e0b3d74aa1557ef74051cVendor (CNA)
Erlang OTP11.2.12.11Vendor (CNA)
Erlang OTP11.6.0.4Vendor (CNA)
Erlang OTP11.7.4Vendor (CNA)
Erlang OTP27.3.4.15Vendor (CNA)
Erlang OTP28.5.0.4Vendor (CNA)
Erlang OTP29.0.4Vendor (CNA)
Erlang OTPe6ff938116b2872bccc478af7fefb56627285b77Vendor (CNA)
Debian:erlang1:27.3.4.1+dfsg-1+deb13u3 · Debian:13Package registry (OSV)
openSUSE:erlang2727.1.3-3.1 · openSUSE:TumbleweedPackage registry (OSV)
Red Hat:erlang270:27.3.4.15-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
SUSE:erlang23.3.4.19-150300.3.39.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7Package registry (OSV)
SUSE:erlang2626.2.1-150300.7.28.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP7Package 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-757 · Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/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.

ATT&CK techniques

Noroxi analysis

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Change log

  1. Fix✗ → ✓

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References

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

All records